Li ni uThc hin n pht trin h thng trng THPT chuyn giai on 2010-2020, nhm nng cao cht lng dy hc trong cc trng THPT chuyn v pht trin chuyn mn cho gio vin dy cc mn chuyn, B Gio dc v o to t chc bin son ti liu Hng dn Th nghim thc hnh trng THPT chuyn mn Ha hc. p ng yu cu i mi dy hc v thi chn hc sinh gii mn ha hc THPT, B Gio dc v o to mi cc cn b qun l ch o dy hc, cc ging vin i hc v cc nh khoa hc c nhiu thnh tch trong cng tc bi dnghcsinhgii vnghincukhoahc, giovintrctipgingdy chng trnh chuyn ha hc tham gia vit cc bi thc hnh. Ni dung cc bi gm cc ch sau:Phn 1. Gii thiu chung v th nghim thc hnh mn ha hcPhn 2. Mt s bi th nghim thc hnh mn ha hcGm 10 bi, mi bi c vit theo cu trc- Mc ch th nghim- C s l thuyt- Dng c, ha cht th nghim- Cc bc tin hnh th nghim- Mt s lu th nghim thc hin thnh cng- Phn tch kt qu th nghim v bo co- Cu hi kim tra v m rngMc d ti liu c vit cng phu, c qua c gp , thm nh v bin tp ni dung nhng khng th trnhkhi cnc nhngs xutnht nh. Cc tc gi mong nhn c gp ca qu thy c.Trn trng cm n.3MC LCNI DUNG TRANGHNG DN S DNG TI LIUPhn 1. Gii thiu chung v th nghim thc hnh mn ha hcA. MT S NH HNG THC HNH TH NGHIMCC MN KHOA HC T NHINI. Vai tr ca dy hc thc hnh i vi hc sinh trng THPT chuynII. Thc trng th nghim thc hnh mn ha hc THPTv cc gii php ci tin thc trng III. Nhng yu cu cn thit cho vic dy thc hnh ha hc c hiu quB. QUY TC LM VIC TRONG PHNG TH NGHIM HA HCI. An ton khi lm vic vi axit v kim II. Quy tc lm vic vi ha cht th nghim C. CC CNH BO V CC NGUY HIM C TH GPV KHUYN CO V AN TON TRONG KHI LM TH NGHIM1. Cnh bo cac nguy c c bi t(K hiu R - Risk)2. Khuy n ca o van toa n (K hiu S - Safety) D. CC PHNG PHP X L CHT THI NGUY HIE. MT S K NNG, THAO TC C BN V CHUN TRONG TH NGHIM THC HNH HA HCPhn 2. Mt s bi th nghim thc hnh mn ha hcBI 1. PHN NG OXI HA KHTh nghim 1: iu ch oxi trong phng th nghimTh nghim 2. Oxi tc dng vi kim loi v phi kimTh nghim 3. Phn ng gia mt s kim loi Fe, Cu vi H2SO4 long hoc c, nng v Phn ng gia kim loi Fe vi dung dch mui CuSO4.Th nghim 4. Phn ng oxi ho - kh nhit cao v nh mi trng. Bi 2.TC PHN NG CN BNG HO HCTh nghim 1. Cc yu t nh hng n tc phn ngTh nghim 2.nh hng ca nhit n cn bng ho hc781213151718202125293237414446504Bi 3.TNH CHT AXIT BAZ CA MT S CHT CHUN AXIT BAZ CN BNG TO PHC TRONG DUNG DCHTh nghim 1. Xc nh pH ca mt s dung dch c cng nng 0,01MTh nghim 2. Chun axit baz, dng ch th qu tm, phenolphtalein, metyl da camTh nghim 3. S to thnh phc cht [Cu(NH3)4]2+ v s phn hy phc cht ny bng axitTh nghim 4. S to thnh kt ta AgCl (t dung dch AgNO3 v dung dch HCl). S ha tan kt ta AgCl bng dung dch NH3Bi 4. NGHIN CU TNH CHT HA HC CA ANDEHIT-XETON, AXIT CACBOXYLICTh nghim 1: Phn ng oxi ha fomandehit bng thuc th Th nghim 2: Tnh cht ha hc c trng ca axetonTh nghim 3: Phn ng este haTh nghim 4: Phn ng iu ch CH3COOH t CH3COONaBi 5.TNH CHT CA MT S CHT HU CTh nghim 1: Xc nh ch s axit ca cht bo Th nghim 2: Phn ng ca glucoz vi thuc th Tolen, Felinh, Benedict v nc bromTh nghim 3: S thy phn ca tinh btTh nghim 4: Mt s phn ng mu ca amino axit v proteinBi 6. THC HNH T CHN V HA HC HU CXc nh hm lng axit axetylsalixylic (CH3COOC6H4COOH) c trong vin thuc aspirinBi 7. PHN TCH NH LNG AXIT ASCORBICTRONG VIN THUC VITAMIN CBi 8. THC HNH T CHN V TNG HP HU C 2 GIAI ON53586567697377818384889294995Giai on 1- iu ch axit benzoic bng PHN NG OXY HA toluen vi KMnO4 nng.Giai on 2- iu ch etylbenzoat bng PHN NG ESTE HABI 9. NHN BIT V TCH CC ION TRONG DUNG DCH BI 9. NHN BIT V TCH CC ION TRONG DUNG DCH9.1. NHN BIT MT S ION THNG DNG C TRONG DUNG 9.1. NHN BIT MT S ION THNG DNG C TRONG DUNG DCH HN HP BNG MT PHN NG DCH HN HP BNG MT PHN NG9.2.TCH V NHN BIT MT S ION THNG DNG THUC CC 9.2.TCH V NHN BIT MT S ION THNG DNG THUC CC NHM PHN TCH KHC NHAU C TRONG DUNG DCH HN HP NHM PHN TCH KHC NHAU C TRONG DUNG DCH HN HPBi 10. CHUN COMPLEXON;Xc nh ion kim loi dng php o complexon.1051091131181216HNG DN S DNG TI LIUCun ti liu ny c s dng cng vi cun Ti liu bi dng pht trin chuyn mn cho gio vin trng THPT chuyn nm 2011 mn Ha hc. C hai iu cn trnh l:- Ch khi no c trang thit b, ha cht, mu vt nh trong ti liu th mi c th tin hnh thc hnh c. Ta c th chn nhng th nghim thc hnh ph hp vi iu kin ca a phng thc hin trc, ng thi c k hoch khc phc kh khn tr ngi thc hin ht cc bi thc hnh trong nhng nm sau.- Nu cho rng ch cn thc hin nh ni dung cc bi thc hnh trong ti liu l tt ri. Nhng ni c iu kin v trang thit b v gio vin c th m rng ni dung bi thc hnh. Trong cun Ti liu bi dng pht trin chuyn mn cho gio vin trng THPT chuyn nm 2011 mn ha hc c gii thiu rt nhiu bi thc hnh khc na. s dng ti liu hiu qu nht xin lu my im sau:- c k ni dung bi thc hnh, cn c vo thc tin a phng quyt nh mc tiu c th cho tng ni dung thc hnh th nghim chn.- Nghin cu phn c s l thuyt ca th nghim thc hnh. y chnh l cn c gii thch cc hin tng quan st c trong th nghim.- Nht nh hc sinh phi thnh tho cc bc: kim tra dng c thit b, ha cht, mu vt; trnh t cc bc lm th nghim thc hnh v phi c hng dn chi tit cc thao tc c bn trong th nghim thc hnh.- Gio vin cn nghin cu tht k ni dung phn tch kt qu th nghim v bo co hng dn hc sinh ghi chp kt qu thc hnh, x l cc s liu thu c, trnh by bo co.- Phn cu hi kim tra v m rng l nhng gi bc u. Trong thc tin dy hc thc hnh gio vin c th a thm nhiu tnh hung mi kch thch t duy cho hc sinh.7Phn 1. Gii thiu chung v th nghim thc hnh mn ha hcA. MT S NH HNG THC HNH TH NGHIM CC MN KHOA HC T NHIN Trong mi nh trng, i ng GV lun l mt trong nhng nhn t quan trng nht gp phn quyt nh s pht trin ca mt nh trng, bi l chnh h l ngi t chc thc hin c hiu qu cc khu ca qu trnh dy hc, gio dc v pht trin chuyn mn, pht trin nh trng. Trong cc trng THPT chuyn, i ng GV ct cn, u n v chuyn mn li cng c vai tr quan trng hn, l nhng nhn t tch cc, l tm gng trong vic rn luyn o c, t hc, sng to pht hin, bi dng nhng hc sinh nng khiu to ngun tip tc o to thnh nhn ti, p ng yu cu pht trin t nc trong thi k CNH, HH, hi nhp quc t. Hn na, trng THPT chuyn c nh hng xy dng thnh y l hnh mu ca cc trng THPT v c s vt cht, i ng GV v t chc cc hot ng gio dc, th i ng GV trng chuyn ni chung, i ng GV ct cn ni ring li cng c v tr rt quan trng. mt kha cnh no , GV ct cn c th coi l nhng GV u n, c nhng phm cht cn thit ca nhng cn b qun l, v vic pht trin i ng GV u n chnh l ngun pht trin i ng CBQL nh trng ph thng v ngnh gio dc v o to trong tng lai. Trong nhng nm qua, i ng GV trng chuyn c hnh thnh t nhiu ngun khc nhau, c ng gp ht sc to ln vo vic pht hin, bi dng nngkhiuchohcsinh; gpphnquantrnglmnnnhngthnhtchrt v vangcahcsinhVit Namtrn utrngtr tu quct. Tuynhin, bn cnh nhng u im rt cn bn, hin nay mt s gio vin chuyn cha p ng c yu cu i mi c v s lng v trnh , thiu cc k nng nghin cu pht trin chng trnh v ti liu; kh nng xc nh mc tiu gio dc v dy hc qua tng bi hc, mn hc cn yu; k nng dy hc, nht l dy hc thc hnh cn hn ch, kh nng NCKH v hng dn hc sinh NCKH cn hn ch. 8Trc bi cnh , vi s tham mu ca B GDT,ngy 24/6/2010,Th tng Chnh ph k Quyt nh s 959/Q-TTg ph duyt n Pht trin h thng trng THPT chuyn giai on 2010-2020. Trong n, ni dung pht trin i ng gio vin, cn b qun l trong cc chuyn c ht sc coi trng. n xc nh: Ch trng xy dng i ng GV u n v hot ng chuyn mn trong h thng trng trung hc ph thng chuyn, to iu kin gip h tr thnh nhng nhn t tch cc, l tm gng trong vic rn luyn o c, t hc, sng to v xy dng mng li hot ng ca i ng ny trn ton quc. C th:(1) B sung, hon thin cc quy nh v c cu, nh mc GV, nhn vin; v cngtctuyndng, lunchuynGVtrngchuyn; banhnhquynh v tiuchunGV,CBQL trng THPTchuyn trnc s chunnghnghip GV,chun hiu trng trng trung hc v cc quy nh khc v GV,CBQL trng THPT; (2) Tin hnh r sot, nh gi, sp xp li i ng CBQL, GV v nhn vin c k hoch tuyn dng, bi dng nhm m bo s lng, cn i v c cu v nng cao trnh chuyn mn, nghip v, nng lc lm vic;(3) Ch trng xy dng i ng GV u n v hot ng chuyn mn trong h thng trng THPT chuyn, to iu kin gip h tr thnh nhng nhn t tch cc, l tm gng trong vic rn luyn o c, t hc, sng to v xy dng mng li hot ng ca i ng ny trn ton quc; (4) Tng cng cng tc bi dng nng cao nng lc chuyn mn, nghip v, tin hc v ngoi ng cho cn b qun l, gio vin trng chuyn.- nh hng ni dung bi dng GV chuyn phhp vi tng giai on. Tng cng vic bi dng cho CBQL v kin thc, knng qun l; bi dng cho GV v i mi PPDH, i mi KTG, nng cao nng lc pht trin chng trnh, ti liu mn chuyn, nng lc t chc cc hot ng gio dc;9- T chc cc kha bi dng ting Anh, tin hc cho CBQL, GV; a i bi dng ting Anh ti nc ngoi cc GV ging dy ting Anh trong cc trng chuyn; - T chc cc kha o to ngn, di hn trong, ngoi nc v ging dy bng ting Anh cho GV dy cc mn ton, vt l, ha hc, sinh hc, tin hc, tng bc thc hin dy hc cc mn hc ny bng ting Anh trong cc trng chuyn;- Xy dng cc din n trn internet GV v HS trao i kinh nghim ging dy vhc tp; t chc cc hi tho trao i kinh nghim gia cc trng chuyn vi cc c s gio dc trong, ngoi nc c o to, bi dng HS nng khiu. thc hin nh hng trn ca n, c nhiu vic phi lm, trong cng tc bi dng nng cao nng lc chuyn mn v nghip v ca i ngu GV c vai tr rt quan trng.B GDT (trc tip l V GDTrH v Chng trnh pht trin GDTrH) t chc Hi tho, tp hun cho CBQL, GV ct cn cc trng chuyn trong c nc ln th 2 Nm 2011 .1. Mc tiu1.1. Thng nht c nh hng ni dung, phng thc bi dng GV trng THPT chuyn giai on 20112015 v k hoch bi dng tng nm.1.2. Trangb choGVmt s ni dungchuyn va thit thcphc v ngay cho vic dy hc trng THPT chuyn;va nng cao tim lc ca gio vin cc trng chuyn (Dy mt s chuyn chuyn su; i mi PPDH,KTG trong trng THPT chuyn; i mi cng tc nh gi hc sinh gii; t chc dy thc hnh.).1.3. Hnh thnh mi lin kt v trao i thng tin, h tr nhau trong ging dy ca cc GV dy mn chuyn gia cc trng chuyn, to c s bc u cho vic hnh thnh mng li GV ct cn gia cc trng chuyn theo khu vc, ton quc.102. Ni dung2.1. T chc Hi tho i ng GV ct cn cc trng THPT chuyn c cng nhau nghin cu, trao i, thng nht nhng ni dung c bn, trng tm v nh hng ni dung, phng thc bi dng GV trng THPT chuyn giai on 2011 2015 v k hoch bi dng tng nm.2.2. T chctphunmt s chuyn vathit thcphcv ngaycho vic dy hc trng THPT chuyn hin nay; va nng cao tim lc ca GV cc trng chuyn. C th: Dy mt schuyn chuyn su;i mi PPDH, i mi KTG;T chc dy thc hnh.2.3. Xy dng c ch lin kt v trao i thng tin, h tr nhau trong ging dy ca cc GV dy mn chuyn gia cc trng chuyn, to c s bc u cho vic hnh thnh mng li GV ct cn gia cc trng chuyn theo khu vc, ton quc. Gp phn Rn luyn mt s phm cht ca ngi gio vin ct cn nh kh nng tchc hot ng, t vn, to ng lc cho ng nghip, x l cc tnh hung lin quan n chuyn mn.Nhng vn trn, cc anh ch em GV ct cn cn nm k c th v tp hun li gip cho mi GV ca trng qun trit trong tng bc ca bi dy, tng bi, tng chng hoc ch , tng lp hc ca tng mn hc; ng thi hng ti vic hnh thnh mt mng li GVu n ton quc. vic tp hun c cht lng,hiu qu cao, B GDT nghBan T chc, cc ging vin thc hin vic tp hun theo phng thc m: Cng nhau t chc, cng nhau xy dng ni dung, cung nhau nh gi v th hng kt qu tp hun; to iu kin h tr ti a cho hc vin trong iu kin c th c. Cc anh ch hc vin cn thc hin nghim tc cc quy nh ca ban t chc nhm m bo kha hc c cht lng, hiu qu v mi hc vin u l cc bo co vin gii ti cc lp bi dng gio vin ti a phng, c s gio dc.Nhn dp ny, thay mt B GDT v Ban t chc, chng ti xin ghi nhn v cm n s gip , h tr ca thy c gio l tc gi ti liu ng thi cng l 11cc bo co vin;cm n cc c quan lin quan gp phn lm cho t tp hun din ra thun li. Xin knh chc cc ng ch i biu, cc thy c gio, cc anh ch sc khe, hnh phc; chc t tp hun thnh cng./.I. Vai tr ca dy hc thc hnh i vi hc sinh trng THPT chuyn Khng th hnh dung c vic ging dy ha hc trong nh trng m li khng c quan st, khng c th nghim hc tp.B.P. Exipp (trong cun nhng c s ca LLDH). Quan st v th nghim l cc phng php nghin cu c bn ca khoa hc t nhin, ca cc mn khoa hc thc nghim, trong c mn ha hc. Ha hc l mt khoa hc v s khng th pht trin c nu khng c quan st, th nghim. Quan st v th nghim to kh nng cho cc nh khoa hc pht hin v khai thc cc s kin, hin tng mi, xc nh nhng quy lut mi, rt ra nhng kt lun khoa hc v tm cch vn dng vo thc tin.i vi qu trnh dy hc cc mn khoa hc t nhin, khoa hc thc nghim, quan st v th nghim cng l phng php lm vic ca hc sinh (HS), nhng vi HS nhng bi tp quan st hoc cc th nghim c gio vin (GV) trnh by hay do chnh cc em tin hnh mt cch c lp (thc hnh quan st,th nghim ca HS) di s t chc, hng dn ca GV thng gii quyt nhng vn bit trong khoa hc, rt ra nhng kt lun cng bit tuy vy i vi cc em HS vn l mi. Thng qua quan st, th nghim, bng cc thao tc t duy phn tch, tng hp, tru tng ha v khi qut ha gip cc em xy dng cc khi nim. Bng cch cc em nm kin thc mt cch vng chc v gip cho t duy pht trin. Quan st v th nghim i hi phi c nhng thit b dy hc nh tranh nh, m hnh, cc mu vt t nhin v cc phng tin thit b phc v cho vic tin hnh cc th nghim. Quan st v th nghim khng ch cho php HS lnh hi tri thc mt cch su sc, vng chc m cn to cho cc em mt ng lc bn trong, thc y cc em thm hng say hc tp. 12Tc ng c cu Trm nghe khng bng mt thy, trm thy khng bng mtlm/ mt s, ni ln vai tr ca quan st th nghim. Ngi n v ngi Trung Hoa cng ni: Nghe th quen, nhn th nh, lm th hiu. Nhng kt qu phn tch trn y khng ch cho chng ta thy r tm quan trngcath nghimthchnhhahc(TNTHHH) mcnnhnmnhn phng php s dng cc TNTHHH nh th no c th t c hiu qu cao, p ng mc tiu dy hc hin nay ca s nghip gio dc. II. Thc trng th nghim thc hnh mn ha hc THPT v cc gii php ci tin thc trng Hin nay s lng v cht lng TNTHHH cha p ng c yu cu ca vic dy hc ni chung v c bit l yu cu vic i mi dy hc ni ring. Tnh trng c th c nhiu nguyn nhn, phn v kinh ph cho khu vc ny cn hn hp tuy c nhiu c gng, phn v trch nhim ca nh sn xut (cn m khng dng c, dng c th cng chng hng), phn v thiu mt s qun l ch o, ng vin nhng ngi tt, vic tt trong s dng v ci tin sng to TNTHHH hin c Nh phn tch, hiu qu dy hc cn ty thuc vo phng php s dng cc TNTHHH. Nu mt bc tranh, mt th nghim ch c s dng minh ha v cng c nhng iu GV trnh by y v phng din l thuyt s hn ch mt t duy sng to ca HS, HS hu nh khng thu lm c thm g v mt kin thc, nu khng phi ch l rn luyn k nng quan st, th nghim. Nhng nu c s dng theo con ng tm ti nghin cu (khm ph) i n kin thc cn lnh hi (kin thc mi) s c ngha khc c bn so vi loi hnh th nghim trn, n gip HS c iu kin, c hi pht trin t duy sng to - mt phm cht v nng lc cn c con ngi mi m nh trng c trch nhim o to. i theo con ng ny, sau khi hiu c nhim v cn lm sng t (mc ch ca th nghim) bng t duy tch cc, HS s hnh thnh c cc gii nh (trong nghin cu khoa hc y chnh l bc xy dng gi thuyt v vn nghin cu (t s ny sinh cu hi: iu g s xy ra nu? Cu hi c 13hnh thnh t nhng lin tng da trn vn kin thc v kinh nghim c ca HS. Khi gi nh c hnh thnh, trong hm cha con ng phi gii quyt, HS d kin k hoch gii quyt chng minh cho gi nh nu. Hai bc nu gi nh v d kin k hoch gii quyt chng minh cho gi nh l hai bc i hi t duy tch cc v sng to. y l nhng c hi rn luyn tu duy sng to cho HS rt tt, l giai on tin hnh th nghim tng tng (thnghim trong t duy) nh hng cho hnh ng th nghim tip theo da trn k hoch c HS thit k (k hoch d kin). Cui cng, cn c vo kt qu ca th nghim, HS rt ra kt lun, nghi l HS lnh hi c kin thc t th nghim m khng phi do thy truyn t v HS tip thu mt cch th ng. Hinnayhuht ccbi thchnhth nghimsinhhcTHPTtrong chng trnh v SGK c b tr cui mi chng ch mang tnh cht cng c minh ha cho cc kin thc l thuyt c trnh by trong cc bi hc ca chng trnh di hnh thc phn ln l by sn tng bc cho HS. Hn na s tit thc hnh quy nh trong chng trnh v SGK cng cn rt hn ch. Ri y, chc chn s tit ny c th s c nng ln cho ph hp vi xu th chung cagiodcthgii vtngngvi tnh cht cacc mnkhoa hc thc nghim. Trc mt trong khi ch i, i hi lng nhit tm v s nghip gio dc ca cc thy c ang tin hnh cc bi thc hnh hin c theo phng thc mi nhng ni dung ph hp v cng c th b sung thm cc th nghim vo cc tit dy khi c th v c iu kin thch hp. Trong ti liu ny, ngoi mt s th nghim thc hnh quen thuc, chng ti s gii thiu mt s th nghim thc hnh c tnh cht gi cc n v tham kho v vn dng trong iu kin c th, cng c th tin hnh hnh thc ngoi kha hoc i n cc c s c iu kin v trang thit b th nghim thc hnh sinh hc hc tp.14III. Nhng yu cu cn thit cho vic dy thc hnh ha hc c hiu quDy thc hnh, mc ch chnh l rn cc k nng thao tc chn tay, cc c tnh kin nhn, bit chp nhn tht bi v t tm cch khc phc tht bi t c mc ch ca mnh. V vy hc sinh phi t mnh lm th nghim cho d cc thao tc ban u cn vng v v thng xuyn tht bi. Nh vy, nu quan nim thc hnh ch l minh ha, trnh din hc sinh xem th vic t chc cho c lp hc sinh vo mt phng th nghim lm cng lc l c nhng hc sinh khng th hnh thnh c k nng cng nh rn luyn c nhng c tnh cn thit ca ngi lm khoa hc. Cn nu hc sinh t lm th li phi chia lp thnh cc nhm nh ti a khong 10 em th cc em mi c th t lm th nghim c v hc sinh ch hnh thnh c k nng khi c lm i lm li nhiu ln mt k nng nht nh.Mt quan nim khng ng v dy thc hnh l gio vin thng khng a ra cc tnh hung khc thng dy hc sinh cch phn tch rt ra cc kt lun phhpcngnhkhngbit cchtm ranguyn nhnkhi th nghimkhng thnh cng. Hc sinh c yu cu phi tm ra nguyn nhn (a ra gi thuyt) v lm th nghim chng minh gi thuyt ca mnh l ng. Nh vy mc ch ct li ca dy thc hnh l rn cc k nng kho lo trong cc thao tc tay chn, cc k nng b tr th nghim, thu thp kt qu, gii thch kt qu thc nghim,l giia ra cc gi thuytv t tin hnh cc th nghim chng minh gi thuyt ca mnh l ng ch khng n thun l minh ha cho cc bi l thuyt. Nh vy dy thc hnh pht trin cc k nng tng hp v do vy tt c cc hc sinh cn c dy thc hnh. Lu l ngay c trong cc k thi Olympic ha hc Quc t c s dng cc trang thit b hin i nh trc quang, in di, sc k, quang ph vv... th im ca hc sinh cao hay thp khng ph thuc vo thit b tr phi hc sinh cha c lm quen vi thit b . V s dng thit b hin i cng ch thu thp s liu, trong khi cc k nng n gin nh pha long ha cht,x l s liu thu cnh v th,rt ra cc kt lun ph hp,bitcch sp xp thi gian hp l vv... li quyt nh kt qu cui cng.Qui trnh cho mt bi th nghim c th gm cc bc nh sau:15- Chun b th nghim: GV phi c k hoch m bo chun b y dng c, ha cht, mu vt v cc iu kin cn thit khc th nghim thnh cng. C th giao cho HS chun b nhng phi kim tra.- Bc 1: GV nu mc tiu th nghim (hoc hng dn hc sinh pht biu mc tiu thc hnh), phi m bo mi HS nhn thc r mc tiu lm th nghim lm g?Ph bin ni qui an ton phng th nghim: Ngay khi bt u mt bi thc hnh, gio vin cn phi hng dn cho hc sinh v qui tc an ton trong phng th nghim.iu ny l ht sc cn thit v phi lm ngay mi ln hc sinh vo phngth nghim.Bncnh cng cn phbin cchcpcu trong nhng trng hp cn thit nh bng ha cht, bng b khi b thng vv...- Bc 2: GV hng dn HS cch tin hnh th nghim, phi m bo mi HS nhn thc r lm th nghim nh th no? Bng cch no?Gio vin gii thiu qui trnh th nghim:Hc sinh c th t c qui trnh th nghim nu c sn trong SGK hoc gio vin gii thiu cho tng hc sinh. Sau hc sinh t kim tra cc loi ha cht thit b, mu vt xem c p ng c vi yu cu bi thc hnh hay khng.Tin hnh th nghim: Hc sinh t tin hnh th nghim theo qui trnh cho thu thp s liu.- Bc 3: M t kt qu th nghim. HS vit ra (hoc ni ra) cc kt qu m h quan st thy trong qu trnh lm th nghim.X l s liu thc nghim: Hc sinh x l s liu v vit bo co th nghim np cho gio vin. Cui bui gio vin c th a ra cc tnh hung khc vi th nghim hc sinh suy ngm v tm cch l gii. Gii thch cc hin tng quan st c: y l giai on c nhiu thun li t chc HS hc theo phng php tch cc. GV c th dng h thng cu hi dn dt theo kiu nu vn gip HS t gii thch cc kt qu.- Rt ra kt lun cn thit: GV yu cu HS cn c vo mc tiu ban u trc khi lm th nghim nh gi cng vic lm.- Ch : Cc th nghim ha hc c th l th nghim nh tnh hay nh lng. Cc th nghim nh tnh th khng nn qu tit kim nguyn liu, s kh 16quan st kt qu. Cc th nghim nh lng th cn chnh xc hm lng cc cht lm th nghim mi c kt qu. - Tm tt quy trnh mt bi thc hnh Bc 1. Xc nh mc tiu (cho GV v cho HS). Yu cu ca bc ny l HS phi nhn thc c v pht biu r mc tiu (tr li cu hi: lm g?) Bc 2. Kim tra kin thc c s v kim tra s chun b thc hnh (tr li cu hi: c lm c khng?). Bc 3. Xc nh ni dung thc hnh (tr li cu hi: lm nh th no?) Bc 4. Tin hnh cc hot ng thc hnh (tr li cu hi: quan st thy g? thu c kt qu ra sao?). Bc 5. Gii thch v trnh by kt qu, rt ra kt lun (tr li cu hi: ti sao? Mc tiu hon thnh hay cha?). Vit bo co thc hnh. B. QUY TC LM VIC TRONG PHNG TH NGHIM HA HCI. An ton khi lm vic vi axit v kim 1. An ton khi lm vic vi axit: - Phi lm vic trong t ht bt c khi no un nng axit hoc thc hin phn ng vi cc hi axit t do. - Khi pha long, lun phi cho axit vo nc tr phi c dng trc tip. - Gi axit khng bn vo da hoc mt bng cch eo khu trang, gng tay v knh bo v mt. Nu lm vng ln da, lp tc ra ngay bng mt lng nc ln. - Lun phi c k nhn ca chai ng v tnh cht ca chng. - Ly axit ng lng ghi trong ti liu, mi axit phi c mung hoc ng ht ring..- Axit ri ra ngoi phi dn ngay, cc axit thi ng ni quy nh.2. An ton khi lm vic vi kim - Kim c th lm chy da, mt gy hi nghim trng cho h h hp. - Mang gng tay cao su, khu trang khi lm vic vi dung dch kim m c. - Thao tc trong t ht, mang mt n chng c phng nga bi v hi kim. 17- Dung dch amoniac: l mt cht lng v kh amoniac rt n da, mang gng tay cao su, khu trang, thit b bo v h thng h hp. Hi amoniac d phn ng mnh vi cht oxi ho, halogen, axit mnh. - Kim loi Na, K, Li, Ca: phn ng cc mnh vi nc, m, CO2, halogen, axit mnh, dn xut clo ca hydrocacbon. To hi n mn khi chy. Cn mang dng c bo v da mt. - Can xi oxit rt n da, phn ng cc mnh vi nc, cn bo v da mt, ng h hp do d nhim bi oxit. - Natri hiroxit v kali hiroxit: rt n da, ta nhit ln khi tan trong nc. Cc bin php an ton nh trn, cho tng vin hoc t bt vo nc ch khng c lm ngc li. -Ly kim ng lng ghi trong ti liu, mi loi kim phi c mung hoc ng ht ring..- Kim ri ra ngoi phi dn ngay, cc kim thi ng ni quy nh.II. Quy tc lm vic vi ha cht th nghim 1. Ho cht th nghim: Cc ho cht dng phn tch, lm th nghim, tin hnh phn ng, ... trong phng th nghim c gi l ha cht th nghim. Ho cht c th dng rn (Na, MgO, NaOH, KCl, (C6H5COOH) ...; lng (H2SO4, aceton, ethanol, chloroform, ...) hoc kh (Cl2 , NH3 , N2 , C2H2 ...) v mc tinh khit khc nhau: - Sch k thut (P): sch > 90% - Sch phn tch (PA): sch < 99% - Sch ha hc (PC): sch > 99% Ha cht c tinh khit khc nhau c s dng ph hp theo nhng yu cu khc nhau v ch nn s dng ha cht cn nhn hiu. 182. Nhn hiu ho cht: Ha cht c bo qun trong chai l thy tinh hoc nha ng kn c nhn ghi tn ho cht, cng thc ha hc, mc sch, tp cht, khi lng tnh, khi lng phn t, ni sn xut, iu kin bo qun. 3. Cch s dng v bo qun ho cht: Khi lm vic vi ha cht, nhn vin phng th nghim cng nh gio vin, hc sinh cn ht sc cn thn, trnh gy nhng tai nn ng tic cho mnh v cho mi ngi. Nhng iu cn nh khi s dng v bo qun ha cht c tm tt nh sau: - Ha cht phi c sp xp trong kho hay t theo tng loi (hu c, v c, mui, axit, baz, kim loi, ...) hay theo mt th t a, b, c khi cn d tm. - Tt c cc chai l u phi c nhn ghi, phi c k nhn hiu ha cht trc khi dng, dng xong phi tr ng v tr ban u. - Chai l ha cht phi c np. Trc khi m chai ha cht phi lau sch np, c chai, trnh bi bn lt vo lm hng ha cht ng trong chai. - Cc loi ha cht d b thay i ngoi nh sng cn phi c gi trong chai l mu vng hoc nu v bo qun vo ch ti. -Dng c dng ly ha cht phi tht sch v dng xong phi ra ngay, khng dng ln np y v dng c ly ha cht.- Khi lm vic vi cht d n, d chy khng c gn ni d bt la. Khi cn s dng cc ha cht d bc hi, c mi,... phi a vo t ht, ch y kn np sau khi ly ha cht xong. - Khng ht bng pipet khi ch cn t ha cht trong l, khng ngi hay nm th ha cht. - Khi lm vic vi axit hay baz mnh: Bao gi cng axit hay baz vo nc khi pha long (khng c nc vo axit hay baz); Khng ht axit hay baz bng ming m phi dng cc dng c ring nh qu bp cao su, pipet my. Trng hp b bng vi axit hay baz ra ngay vi nc lnh ri bi ln vt bng NaHCO3 1% (trng hp bng axit) hoc CH3COOH 1% (nu bng baz). Nu b bn vo mt, di mnh vi nc lnh hoc NaCl 1%. Trng hp b ha cht vo ming hay d dy, nu l axit phi sc ming v ung nc lnh c NaHCO3, nu l baz phi sc ming v ung nc lnh c CH3COOH 1%. 19C. CC CNH BO V CC NGUY HIM C TH GP V KHUYN CO V AN TON TRONG KHI LM TH NGHIM1. Cnh bo cac nguy c c bi t(K hiu R - Risk)R 1. Gy nkhi da ng kh.R 2. Nguy c nkhi va p, ma sa t, cola ho c ngu n gy cha y kha c.R 3. Nguy c gy nr t cao khi va p, ma sa t, cola ho c ngu n gy cha y kha c.R 4. Ta o ra cac h p ch t nkim loa i r t nha y.R 5. un no ng cothgy n.R 6. Gy nkhi ti p xuc hoc khng ti p xu c vi khng khi .R 7. Cothgy cha y. R 8. Ti p xu c vi v t li u cha y cothgy cha y. R 9. Gy nkhi tr n vi ch t dcha yR 10. Cothcha y.R 11. R t dcha y.R 12. D cha y.R 13. Khiho a lo ng rt dcha y.R 14. Pha n ng ma nh li t vi n c. R 15. Ti p xu c vi n c gia i pho ng khidbc cha y. R 16. Gy nkhi tr n vi ca c ch t oxi ho a.R 17. Tbc cha y trong khng khi . R 18. Khi s du ng, cothtao ra hn h p hi v i khng khigy cha y hoc n.R 19. Cothtao ra ca c peoxit gy n.R 20. Nguy hi m khi hi t va o.R 21. Nguy hi m khi ti p xuc v i da.R 22. Nguy hi m nu nu t va o.R 23. Ngc khi hi t va o. 20R 24. Ngc khi ti p xuc v i da.R 25. Ngc n u nut va o. R 26. R t c khi hit va o. R 27. R t c khi ti p xu c vi da. R 28. R t c nu nu t va o. R 29. Ti p xu c vi n c gia i pho ng khic. R 30. Khi s du ng, cothr t dcha y.R 31. Ti p xu c vi axit gia i pho ng khic. R 32. Ti p xu c vi axit gia i pho ng khir t c.R 33. Gy nguy hi m do ca c tac ng tich lu y.R 34. Gy bo ng. R 35. Gy bo ng nng.R 36. Gy cay mt. R 37. D ng cho hh h p. R 38. Gy m n ng a da. R 39. Nguy hi m do ca c ta c ng nghim tro ng khng thloa i bo.R 40. Cothnguy hi m do cac ta c ng nghim tro ng khng thloa i bo.R 41. Nguy hi m do gy ho ng m t nng.R 42. Cothgy smu i khi hit va o.R 43. Cothgy m n ng a khi ti p xu c vi da.R 44. Nguy c gy nnu un nong trong bi nh ki nR 45. Coth gy ung th. R 46. Coth gy tn hai gen.R 47. Coth gy tn hai phi. R 48. Nguy hi m do bit n ha i ke o da i. .2. Khuyn cao v an toa n (K hiu S - Safety) S 1. Nu t ki n bi nh ch a.21S 2. ca ch xa t m v i cuatrecon. S 3. Gini thoa ng ma t. S 4. Ba o qua n ca ch xa khu dn c.S 5. Ba o qua n bi nh ch a di ca c iu ki n....(ch t lo ng c nhasa n xu t a ra chidn ring).S 6. Ba o qua n di ca c iu ki n... (khitr c nhasan xut chidn ring).S 7. Ba o qua n bi nh ch a da ng o ng ki n. S 8. Ba o qua n bi nh ch a kh ra o.S 9. Ba o qua n bi nh ch a ni thng gio .S 10. Ba o qua n bi nh ch a ch t trong bi nh da ng t. S 11. Tra nh ti p xu c vi khng khi .S 12. Khng bao qua n binh cha da ng ki n. S 13. Ba o qua n ca ch xa thc ph m, n c u ng vathc ph m cho gia suc.S 14. Ba o qua n ca ch xa ..... ( cac ch t kinhau pha i c nhasan xu t chiinh).S 15. Ba o qua n ca ch xa nhi t. S 16. Ba o qua n ca ch xa ngu n pha t l a. C m hut thu c.S 17. Ba o qua n ca ch xa ca c ch t dcha y.S 18. Ti p xuc vambi nh ch a hoach t cn th n.S 20. Khi sdung ho a ch t khng n hoc u ng ng thi.S 21. Khi sdung ho a ch t khng hut thu c. S 22. Khng hit bui ho a ch t.S 23. Khng hit khi /kho i/ hi/ khiphun sng.S 24. Tra nh ti p xu c hoa ch t v i da.S 25. Tra nh hoa ch t bn va o mt. S 26. Trong trng hp bib n va o m t, pha i ra ngay vi nhi u n c van c quan y t.S 27. C i bongay ao qu n binhi m b n ho a ch t.S 28. Khi bidi nh va o da, r a ngay v i m t l ng nhi u.....(do nhasa n xu t chii nh).22S 29. Khng lam kh ki t bi nh ch a. S 30. Khng bao gic cho n c va o san ph m nay.S 31. Ba o qua n ca ch xa ca c ch t gy cha y. S 33. C n coca c bi n pha p pho ng spho ng i n.S 34. Tra nh va p vama sa t.S 35. Ch t na y vabinh cha nopha i c loa i botheo cach an toa n thi ch hp.S 36. M c qu n ao bao vthi ch h p.S 37. eo gng tay thi ch h p.S 38. Trong tr ng hp khng u thng thoa ng, pha i eo thi t bitrh h p.S 39. eo phng ti n bao vmt/ mt.S 40. vsinh sa n vaca c v t du ng binhi m bn hoa ch t na y, c n sdu ng ... (do nhasa n xu t chiinh).S 41. Trong tr ng hp cha y va / hoc nkhng c hit kho i. S 42. Trong thi gian phun kho i / phun sng pha i eo thi t bitrh h p thi ch hp.S 43. Trong tr ng h p cha y, sdu ng ....(chirochi nh xa c du ng loa i du ng cuc u ho a na o. N u n c la m tng nguy c thikhng bao gi c du ng n c) S 44. Nu ca m th y ngi khng kho e, n c quan y tngay (cobi n chid n) S 45. Trong tr ng hp tai na n ho c n u ngi khng c kho e n c quan y tngay (cobi n chid n). 3. V d v ngha R v SAxetonCng thcC3H6OKhi lng phn t 58,08im nng chy95 oCim si 56 oCKhi lng ring0,79 g/cm3R11 Rt d chy23S9 Gi bnh cha ni thng thongS16 Trnh xa ngun laS23 Khng hi t khi /kho i/ hi/kh phun sngS33 Thc hin cc bin php phng nga chng phng tnh inAxit clohidricCng thcHClKhi lng phn t 36,46Khi lng ring 1,200 g/cm3R34 Nguyn nhn bngR37 D ng cho h h hpS26 Trong trng hp tip xc vi mt, ra sch ngay vi tht nhiu nc v tm kim y t t vnS36 Mc qun o bo h ph hpS45 Trong trng hp xy ra tai nn hoc nu bn cm thy khng c khe, tm t vn y t ngay lp tc (mang theo nhn hiu nu c th)MetanolCng thcCH4OKhi lng phn t 32,04im nng chy98 oCim si 65 oCKhi lng ring0,79 g/cm3R11 Rt d chyR23-25 c khi ht phi, tip xc vi da v nu nut phiR39/23/24/25c hi: nguy c nh hng rt nghim trng khng th o ngc qua ng h hp, tip xc vi da v nu nut phiS7 Gi bnh cha ng knS16 Trnh xa ngun la Cm ht thuc 24S36/37 Mc qun o bo h ph hp v eo gng tayCht c (T) v rt c (T+)Cht d chy (F) v rt d chy (F+)Cht d bt la (Xi) v c (Xn)Cht gy n (E)Cht oxi ha mnhCht n mn (C)Cht gy nguy him vi mi trng (N)Hnh 1. K hiu biu din mt s cnh bo nguy himD. CC PHNG PHP X L CHT THI NGUY HIKhi cha thc hin chng trnh gim thiu cht thi, lng cht thi sinh ra ln v tch ly ngy cng nhiu. Khi trin khai cc bin php gim thiu, tn dng cht thi, lng cht thi gim i ng k nhng chng vn tn ti trong mi trng. Do , chng ta vn cn phi tin hnh x l, thi b cht thi mt cch an ton, theo cc phng php c trnh by di y:Phn loi rc thiRc thi hin nay ang l mt vn nan gii ca x hi v mi trng, phn loi rc thi to thun li hn cho qu trnh x l, ti ch v lm gim tc ng ti mi trng. M hnh phn loi rc nn thc hin theo tng bc. Bc 1 l phn loi c hai loi rc thi l v c v hu c; 25 Bc 2 l phn loi c ba loi rc thi l hu c, v c c th ti ch v v c khng th ti ch, c hi.Khi mi thc hin phn loi rc thi s c loi rc c phn loi v rc cha c phn loi v vy loi rc cha c phn loi s c thu gom ring. Rc sau khi c thu gom c vn chuyn ti nh my ch bin rc thi; ch bin phn bn nng nghip t rc hu c, gch xy dng t nhng rc thi ph liu nh , siCc phng php ho hc v vt lX l cht thi nguy hi bng phng php vt l nhm tch cht nguy hi ra khi cht thi bng cc phng php tch pha.X l cht thi nguy hi bng phng php ho hc nhm thay i tnh cht ho hc ca cht thi chuyn n v dng khng nguy hi.1. Lc. Lc l phng php tch ht rn t dng lu cht (kh, lng hay kem nho) khi i qua mi trng xp (vt liu lc). Cc ht rn c gi li vt liu lc. Qu trnh lc c th thc hin nh chnh lch p sut gy bi trng lc, lc ly tm, p sut chn khng, p sut d.2.Kt tu.Kt tu l qu trnh chuyn cht ho tan thnh dng khng tan bng cc phn ng ho hc to ta hay thay i thnh phn ha cht trong dung dch (thay i pH), thay i iu kin vt l ca mi trng (h nhit ) gim ho tan ca ho cht, phn khng tan s kt tinh. Phng php kt tu thng dng kt hp vi cc qu trnh tch cht rn nh lng cn, ly tm v lc.3. Oxy ho kh. Phn ng oxy ho kh l phn ng trong trng thi oxy ho ca mt cht phn ng tng ln trong khi trng thi oxy ho ca mt cht khc gim xung. Cht cho electron l cht kh, cht nhn electron l cht oxy ho. thc hin qu trnh oxy ho kh, ngi ta trn cht thi vi ho cht x l (tc nhn oxy ho hay kh) hay cho tip xc cc ho cht cc dng dung dch vi ho cht th kh.264.Bayhi.Bayhi llmccht thi dnglnghayhuynphbng phng php cp nhit ho hi cht lng. Phng php ny thng dng trong giai on x l s b gim s lng cht thi cn x l cui cng.5. ng rn v n nh cht thi. ng rn l lm c nh ho hc, trit tiu tnh lu ng hay c lp cc thnh phn nhim bng lp v bn vng to thnh mt khi nguyn c tnh ton vn cu trc cao. Phng php ny nhm gim tnh lu ng ca cht nguy hi trong mi trng; lm cht thi d vn chuyn do gim khi lng cht lng trong cht thi v ng rn cht thi; gim b mt tip xc cht thi vi mi trng trnh tht thot cht thi do lan truyn, r r, hn ch ho tan hay kh c cc thnh phn nguy hi. ng rn l qu trnh b sung vt liu vo cht thi to thnhkhi rn. Trong c th c cc lin kt ho hc gia cht c hi v ph gia. n nh l qu trnh chuyn cht thi thnh dng n nh ho hchn. Thut ng ny cng bao gm c ng rn nhng cng bao gm c s dng cc phn ng ho hc bin i cc thnh phn cht c hi thnh cht mi khng c. C nh ho hc l bin i cht c hi thnh dng mi khngc. Bao gi l qu trnh bao ph hon ton hay s dng hng ro baoquanh khi cht thi bng mt cht khc. Cht kt dnh v c thng dng l ximng, vi, pozzolan, thch cao, silicat. Cht kt dnh hu c thng dng l epoxy, polyester, nhc asphalt, polyolefin, ure formaldehyt.Cc phng php nhit1.Phng php t.Qu trnh t l mt qu trnh bin i cht thi rn di tc dng ca nhit v qu trnh oxi ha ho hc. t l qu trnh oxy ho nhit cao bng oxy khng kh, bng cch t cht thi ta c th gim th tch ca n n 80-90%; Nhit bung t phi cao hn 800oC, sn phm sau cng bao gm kh c nhit cao bao gm nit v cacbonic, hi nc, v tro. Nng lng c th thu hi c t qu trnh trao i nhit do kh sinh ra c nhit cao.27t thng quay. L t thng quay c s dng x l cc loi cht thi nguy hi dng rn, cn, bn v cng c th dng lng. Thng quay hot ng nhit khong 1100oC.t bng phng php phun cht lng. Cht thi nguy hi dng lng c t trc tip trong l t bng cch phun vo vng ngn la hay vng chy ca l phthucvonhit tr cht thi. Lt cduytr nhit khongtrn 1000oC. Thi gian lu ca cht thi lng trong l t vi phn giy n 2,5 giy.t c xc tc. S dng xc tc cho vo l t tng cng tc oxy ho cht thi nhit thp hn so vi l t thng thng ( 0(khng mu)(mu nu )Gi tr 58 kJ l nhit ca phn ng thun, phn ng thu nhit. Phn ng nghch l phn ng to nhit vi H = 58 kJ < 0.Khi hn hp kh trn ang trng thi cn bng, nu un nng hn hp kh mu nu ca hn hp kh m ln, ngha l cn bng chuyn dch theo chiu thun, chiu ca phn ng thu nhit. Nu lm lnh hn hp kh, mu ca hn hp kh nht i, ngha l cn bng chuyn dch theo chiu nghch, chiu ca phn ng to nhit.Nh vy khi tng nhit , cn bng chuyn dch theo chiu phn ng thu nhit, ngha l chiu lm gim tc dng ca vic tng nhit v khi gim nhit , cn bng chuyn dch theo chiu phn ng to nhit, chiu lm gim tc dng ca vic gim nhit .III. Dng c, ha cht th nghimDNG C HA CHT ng nghim c nhnh, gi ng nghim; Nt cao su; ng dn cao su; kha thy tinh; Chu thy tinh; NO2 (kh); (R20/22/25/26/39 S1/2/7/13/18/23/29/36) Nc 51IV. Cc bc tin hnh th nghimLp mt dng c gm hai ng nghim c nhnh (a) v (b), c ni vi nhau bng mt ng nha mm, c kho K m (hnh 11).Np y kh NO2 vo c hai ng (a) v (b) nhit thng. Nt kn c hai ng, mu ca hn hp kh trong cn bng c hai ng (a) v (b) l nh nhau. ng kho K li ngn khng cho kh hai ng khuch tn vo nhau. Ngm ng (a) vo nc . Mt lt sau ly ra so snh mu ng (a) vi ng (b).V. Mt s lu th nghim thc hin thnh cng Cn thn khi iu ch NO2 v np vo hai ng nghim (a) v (b). Kh NO2 c nn cn ch n cnh bo nguy him v gi an ton khi th nghim. S dng nt cao su va kht vi ming ng nghim v kim tra nt tht cht sau khi np kh. Kim tra k kha thy tinh v ng dn cao su sao cho tht kn. C th thay chu nc bng cch s dng n cn un nh ng (b). VI. Phn tch kt qu th nghim v Bo co Sau khi ngm ng (a) vo nc mt thi gian ta thy mu ng (a) nh th no? Trnh by cn bng ha hc gii thch hin tng trn? Nu kt lun v nh hng ca nhit n s chuyn dch cn bng ha hc.VII. Cu hi kim tra v m rng1) Nu khi lp dng c m nt cao su b h th xy ra hin tng g?2) Nu ngm ng (a) vo nc m kha K khng ng th hin tng xy ra nh th no? Gii thch.52 Hnh 11. Th nghim nhn bit s chuyn dch cn bng ca phn ng2NO2 (k) N2O4 (k)3) Thay th vic ngm ng (a) vo nc bng un nng nh ng (b) c g khc khng? Gii thch4) Trong sn xut ammoniac, yu t nhit c s dng nh th no chuyn dch cn bng sang chiu thun?Bi 3.TNH CHT AXIT BAZ CA MT S CHT CHUN AXIT BAZ CN BNG TO PHC TRONG DUNG DCHTh nghim 1. Xc nh pH ca mt s dung dch c cng nng 0,01MI. Mc ch th nghim Bit pH ca cc axit mnh, yu; cc baz mnh, yu; cc dung dch mui khc nhau nh th no? K nng s dng my o pH So snh kt qu o pH bng my vi kt qu tnh ton theo l thuyt thy s khc nhau gia l thuyt v thc nghim.II. C s l thuyt1. Cch tnh pH ca dung dch axit mnh mt ncV d: dung dch HCl nng mol/l l Ca. Trong dung dch cHCl + H2O Cl + H3O+2H2O OH + H3O+Theo nh lut bo ton proton ta c: [H3O+] = Ca + 2+3 1 ] Gii phng trnh bc 2 tm [H3O+] ri tnh pH = lg[H3O+]Nu dung dch c Ca > 3,16 107 th c th b qua [H3O+] do nc in li ra, nn [H3O+] =Cav pH = lg Ca2. Cch tnh pH ca dung dch baz mnh mt ncV d: dung dch NaOH nng mol/l l Cb. Trong dung dch c53NaOH OH + Na+2H2O OH + H3O+Theo nh lut bo ton proton ta c: [H3O+] + Cb = 2+3 1 ]Gii phng trnh bc 2 tm [H3O+] ri tnh pH = lg[H3O+]Nu dung dch c Cb > 3,16 107 th c th b qua [OH] do nc in li ra, v [OH] =Cbv pOH = lg Cbhay pH = 14 pOH = 14 +lg Cb

3. Cch tnh pH ca dung dch axit yu mt ncV d: dung dch HA nng mol/l l Ca. Trong dung dch cHA + H2O A + H3O+(1)2H2O OH + H3O+(2)Theo nh lut bo ton proton v cc hng s Ka, K2ta c: [H3O+]3 + Ka [H3O+]2 (Ka Ca + K2)[H3O+] Ka K2 = 0Dng phng php gn ng vi sai s pH 005 trong cc iu kin sau:* Nu Ka Ca > 1012 v 0,1 < aaCK < 100 th b qua (2). Ch xt (1):HA + H2O A + H3O+(1)[]Ca x xxvi 0 < x< Ca Ka=axC x 2 Gii phng trnh bc 2 tm [H3O+] ri tnh pH * Nu Ka Ca > 1012 vaaCK > 100 th coi Ca x Ca vKa= axC2 [H3O+] =a aK C 544. Cch tnh pH ca dung dch baz yu mt ncV d: dung dch NH3 nng mol/l l Cb. Trong dung dch cNH3 + H2O OH + NH+4

(1)2H2O OH + H3O+(2)Theo nh lut bo ton proton v cc hng s Kb, K2ta c: Kb [H3O+]3 + (Kb Cb + K2) [H3O+]2 Kb K2[H3O+] (K2)2 = 0Dng phng php gn ng: * Nu Kb Cb > 1012 v 0,1 < bbCK < 100 th b qua (2). Ch xt (1):NH3 + H2O OH + NH+4

(1)[]Cb x xxvi 0 < x< Cb Kb=bxC x 2 Gii phng trnh bc 2 tm [OH] ri tnh pH * Nu Kb Cb > 1012 vbbCK > 100 th coi Cb x Cb vKb= bxC2 [OH] =b bK C 5. Cch tnh pH ca dung dch muiV d: dung dch NH4Cl nng mol/l l Cm. Trong dung dch cNH4Cl NH+4 + Cl

nn[NH+4] = [Cl] = CmDo NH+4 l axit lin hp ca baz yu NH3 nn b thy phn: NH+4 + H2O NH3 + H3O+vi Ka1 = +3 3+4[][][](3)Tng t, dung dch NaF l mui ca axit yu v baz mnh nn:F +H2O HF+ OH vi Ka2 = FHF +3[ ][][ ] (4)55* Xt dung dch NH4F c:NH+4 + H2O NH3 + H3O+

F +H2O HF+ OH 2H2O OH + H3O+Nu Ka Cm ca NH+4 >> 1014 vKb Cm ca F>> 1014 th phn ng ch yu trong dung dch l: NH+4 + F

NH3 + HF[] C x C x xxNgha l: [NH+4] = [F] v [NH3] = [HF]; thay vo (3) (4) c:Ka1 Ka2= [H3O+]2 [H3O+] = a aK K 1 2Trng hp ny pH ca dung dch khng ph thuc vo nng ca muiIII. Dng c, ha cht th nghimDNG C HA CHT ng nghim, gi ng nghim; My o pH; HCl 0,01M;(R34/37-S26/36/45) NaOH 0,01M; (R35-S1/2/26/37/ 39/45) CH3COOH 0,01M; (R10/35-S1/2/23/26/ 45) NH3 0,01M (R10/23/34/50-S1/2/16/36/37 /39/45) CH3COONa 0,01M; (S22/24/25) NH4Cl 0,01 M. IV. Cc bc tin hnh th nghimChun ha my o pH: y l thao tc cn thit trc khi o pH (hoc hng tun) hiu chnh cc sai s gy ra do s thay i yu t ha hc ca in cclmchothmngkhnglpli gitr trckhi xydngng chun. Cc dung dch m c pH = 4.01; 7.00 v 10.01 thng c dng. C th hiu chnh theo phng php hai im hoc 1 im v ty vng gi tr pH cn o. 56 Dng my o pH nhng vo cc dung dch v ghi li tr s pH ca tng dung dch.V. Mt s lu th nghim thc hin thnh cng dung dch trong ng nghim trn gi v khng di chuyn Nhng my o pH vo cc dung dch vi thi gian nh nhauVI. Phn tch kt qu th nghim v Bo co Dung dch axit mnh HCl c pH ? . Gii thch. Dung dch baz mnh NaOH c pH ? . Gii thch. Dung dch axit yu CH3COOH c pH ? . Gii thch.Ka(CH3COOH) = 1,8 105 Dung dch baz yu NH3 c pH ? . Gii thch.Kb(NH3) = 1,8 105 Dung dch mui CH3COONa c pH ? . Gii thch. Dung dch mui NH4Cl c pH ? . Gii thch.VII. Cu hi kim tra v m rng1) p dng l thuyt tnh pH ca tng dung dch. So snh vi kt qu o c theo thc nghim v gii thch.2) Axit c trong hm m (Acid Mine Drainage gi tt l AMD) lm cho nc c pH thp,nh hng n cht lng ngun nc trn th gii. Ni Iron M pH nc l 3,6. Oxi v nc phn ng vi b mt ca pirit st FeS2 to thnh dung dch axit 4FeS2 + 15O2 + 2H2O 4Fe3+ + 8SO42- + 4H+Ti pH = 3,6, nng mol ca ion H+ c to thnh bi AMD lA. 10 3,6 M B. 6 103 MC.6 103 MD. 3980 M 3)Nc ly t mt qung hm m c pH = 0. Hy tnh lng Ca(OH)2 cn dng trung ha mu 1 lt nc trn? A. 0 g B. 37,0 g C. 74,0 g D. 148 g. 574) Tnh axit ca cc dch lng trong c th bin i nh sau:Dch lng Dch bao t Nc bt Mu Rut nonTr s pH 1,6 1,8 6,4 6,8 7,35 7,45 9,0Dung dch no sau y c pH bng vi pH ca dung dch H2SO4 0,1mol.L-1A. Dch bao t. B. Nc bt. C. Mu.D. Rut non.Th nghim 2. Chun axit baz, dng ch th qu tm, phenolphtalein, metyl da camI. Mc ch th nghim Nm c nguyn tc ca phng php chun axit baz thng qua chun dung dch HCl bng dung dch chun NaOH. Rn luyn k nng s dng buret, pipet, pha dung dch chun, chun dung dch, xc nh im tng ng, tnh sai s chun II. C s l thuyt1. Nguyn tc chungChun axit baz, hay cn gi l chun trung ho, l phng php phn tch chun c s dng rt rng ri xc nh nng cc dung dch axit v cc dung dch baz. Trong phng php ny ngi ta dng dung dch kim (NaOH hoc KOH) bit chnh xc nng lm dung dch chun chun dung dch axit v dng dung dch axit mnh (HCl, H2SO4, HNO3) bit chnh xc nng chun dung dch baz. Thc cht cc phn ng chun l phn ng trung ho.Th d,chun dung dch HClcha bit nng bng dung dch chun NaOH : HCl +NaOH NaCl + H2O (1)Chun dung dch CH3COOH bng dung dch chun NaOH : CH3COOH + NaOH CH3COONa + H2O (2)Chun dung dch NH3 bng dung dch chun HCl :NH3 + HCl NH4Cl (3) 58Trong qu trnh chun , pH ca dung dch thay i lin tc. Ti im tng ng,tc l thi im m dung dch chun va trung ho ht dung dch axit hoc baz cn chun , pH ca dung dch ph thuc vo bn cht ca axit hoc baz cn chun v nng ca chng. Vi phn ng (1), pH ti im tng ng l pH ca dung dch NaCl bng 7,0 v khng ph thuc vo nng ca NaCl. pHti imtng ng ca phn ng (2) l pHca dung dch CH3COONa (baz yu), nn pH ln hn 7. pH ti im tng ng ca phn ng (3) l pH ca dung dch NH4Cl (l axit yu), nn pH nh hn 7. nhn ra im tng ng ca phn ng chun , ngi ta dng cht ch th gi l cht ch th axit baz hay cht ch th pH. l axit hu c hoc baz hu c yu c mu sc ca phn t v ca ion khc nhau, nn mu ca cht ch th ph thuc vo pH ca dung dch. C 3 cht ch th thng c s dng l: Phenolphtalein, metyl da cam hoc metyl .* Phenolphtalein l axit 2 nc, trong mi trng axit hoc trung tnh tn ti dng lacton khng mu, khi phn li proton mi u chuyn thnh anion cacboxylatkhng mu, sau chuyn v ni phn t thnh quinonphenolat c mu tm;

OHOHHOCOCOLacton, khng muH2OH2O +OH HOCCOOHKhng muH+OH

OHOH HOCCOOOHH+O OCCOOOHH+Khng mu Quinonphenolat, mu tm59Trong dung dch kim mnh li chuyn sang dng cacbinol khng mu. OHOCCOOOKhng mu* Metyl da cam (heliantin) c tn ha hc l: Natri paradimetylaminoazo-benzensunfonat H3CH3CN N N SO3NaTrong mi trng kim v mi trng trung tnh, c mu vng ca anion H3CH3CN N N SO3Trong mi trng axit c mu ca ion lng ccH3CH3CNH N N SO3H3CH3CN N NH SO3++* Metyl c tn ha hc l: axit para-dimetylamino-azobenzen-o-cacboxylic

H3CH3CN N N COOHBng sau y ghi khong pH i mu ca 3 cht ch th thng c s dng nhiu trong chun axit- baz.Tn cht ch thKhong pH i muMu dng axit - dng bazMetyl da cam 3,1 4,4 VngMetyl 4,2 6,3 VngPhenolphtalein 8,3 10,0 Khng mu- 60Vi mi phn ng chun axit baz ngi ta chn cht ch th no c khongpHi mutrnghocrt st vi pHcaimtngngcas chun .Khi chun trnh nhng sai s ln, ngi ta dng cc dung dch chun c nng gn vi nng ca dung dch cht cn xc nh. Th d, gi s phi chun 20,00 ml dung dch HCl 0,100M bng dung dch chun NaOH. Trong trng hp ny ta khng nn dng dung dch NaOH c nng ln, th d 1,00M. Trong trng hp ny im tng ng s t c khi thm vo 20,00 0,1001,00 = 2,00 (ml) dung dch NaOH 1,00M. Trong trng hp , nukhi chod1git dungdchchuncthtch0,05ml th sai ssl 0,05.100 2,5%2 . V th, ta nn dng dung dch NaOH 0,100M chun th khng mc cc sai s ln.2. Chun dung dch HCl bng dung dch chun NaOHTrc ht ta hy xt s bin thin pH trong qu trnh chun . Gi s ta chun Vml dung dch HCl nng Co mol/l bng dung dch chun NaOH nng C mol/l.Phn ng chun :HCl+ NaOH NaCl + H2O(1)Trc im tng ng, khi thm V ml dung dch NaOH vo, nng ion H+ c tnh theo cng thc : o ooC V CV[H ]V V++(2)Ti im tng ng, ta c dung dch NaCl c pH = 7.Sau im tng ng, tc l khi thm vo lng d dung dch NaOH, th : o ooC V CV[OH ]V V+(3)pOH = - lg [OH-];pH = 14 pOH (4) 61Th d, p dng cc cng thc trn, khi chun 100 ml dung dch HCl 0,100M bng dung dch chun NaOH 0,100M, ta tnh c pH trong qu trnh thm dn dung dch chun NaOH vo v cc kt qu c ghi trong bng sau : VNaOH0 10 50 90 99 99,9 100 100,1 101 110pH 1 1,1 1,48 2,28 3,30 4,30 7,0 9,70 10,7 11,68Nh vy, xung quanh im tng ng c mt s thay i pH rt t ngt : Khi thm 99,9 ml NaOH vo tc l khi chun 99,9% lng axit th pH ca dung dch bng 4,3. Khi thm vo 100,1 ml NaOH tc l khi chun qu 0,1% th pH ca dung dch bng 9,7 tc l bc nhy pH l 5,4 n v pH. Nu ta chn cc cht ch th no c khong i mu nm trong khong t 4,3 n 9,7 kt thc chun th sai s khng vt qu 0,1%. Ta thy trong trng hp ny c th dng c 3 cht ch th metyl da cam, metyl v phenolphtalein lm cht ch th. Cch tnh: Nng mol ca dung dch HCl c tnh theo cng thcNaOH NaOHHClHClV .CCV3. Sai s chun :Sai s chun l t s % gia lng cht chun cho d (+) hoc cho cn thiu () so vi lng cn thit chun n im tng ng.q = wK C Chh C C+ _ ,

(trong : h l [H+]; Co l nng baz; C l nng axit)62III. Dng c, ha cht th nghimDNG C HA CHT B th nghim phn tch th tch (buret, pipet, bnh tam gic) Gi th nghim Dung dch HCl;(R34/37-S26/36/45) Dung dch chun NaOH; (R35-S1/2/26/37 /39/45) Cht ch th phenolphtalein hoc metyl da cam. IV. Cc bc tin hnh th nghim1. Cch pha dung dch chun t cht gc, ngi ta cn mt lng xc nh ph hp cht gc trn cn phn tch c chnh xc 0,0001 hoc 0,00001g, ho tan nh lng lng cn trong bnh nh mc c dung tch thch hp ri pha long bng nc ct hoc dung mi thch hp ti vch mc.Th d: pha dung dch chun NaOH 0,0500 M (M = 40), trc tin cn tnh khi lng NaOH cn thit pha ch c 250 ml dung dch NaOH nng 0,0500M theo cng thc: m= 0,250 0,05 40 = 0,50 gam.Cn 0,50 gam NaOH c tinh khit phn tch trong cc cn trn cn phn tch, chuyn cht rn qua phu vo bnh nh mc 250,0 ml. Trng cc cn 3 ln bng nc ct vo bnh nh mc. Thm khong 150ml nc ct na v lc k cho tan ht sau thm nc ct n vch mc, lc k trn u, ta c dung dch chun NaOH 0,0500M.2.Cch chun :Ly dung dch chun NaOH vo buret. Ly dung dch HCl cn xc nh nng vo bnh tam gic sch (dng pipet).Thm vo 1 - 2 git cht ch th, th d phenolphtalein.Thm t t dung dch chun vo bnh (va thm va lc trn) n khi dung dch cht ch th chuyn mu t khng mu sang mu hng th kt thc. c th tch dung dch chun tiu tn.Tin hnh chun t 2 n 3 ln, ghi cc kt qu v tnh gi tr trung bnh.V. Mt s lu th nghim thc hin thnh cng63 Pha dung dch chun cn thn Cc thao tc s dng pipet v buret phi thnh tho, nn s dng trc khi chun chnh thc (nu kha buret b kt cn nh 1 -2 git glyxerol) Khi cht ch th nhum mu hng, cn lc k, nu mu hng bin mt th thm cn thn tng git nh dung dch chun ng thi lc bnh n khi chc chn mu hng khng bin mt th kt thc.VI. Phn tch kt qu th nghim v Bo co V d: Tnh chnh xc nng dung dch HCl, bit rng khi chun 50,00 ml dung dch ny phi dng ht 30,00 ml dung dch chun NaOH 0,0500M lm i mu metyl da cam t sang vng (pT = 4,4); pT l ch s chun ca cht ch th, php chun thng kt thc ti gi tr pH = pT. Nng gn ng (thc nghim, CoTN) ca HCl:CoTN= , ,, 0 0500 30 0050 00= 0,0300 MSai s chun : q = 104,4 , ,, ,+ 40 0500 0 03005 00 3 00 10 = 2,1 103Nng chnh xc ca HCl:Co(HCl) = 0,0300 + 0,03002,1 103= 0,03006 MVII. Cu hi kim tra v m rng1) Khi chun , s dng buret thng c hin tng qu tay hoc non tay. Sau khi chun , tnh sai s chun nhn c gi tr q < 0 hoc q > 0; hy cho bit ngha ca cc gi tr ny trong chun ?2) nh gi sai s khi chun dung dch NaOH 0,02 M bng HCl 0,1 M, nu kt thc chun ti pT = 4,0?3) Chn cht ch th thch hp trong s: metyl da cam, metyl , phenol , phenolphtalein xc nh im tng ng ca php chun dung dch NH3 0,03 M bng HCl 0,06 M. Bit: Ka(NH+4 = 5,75 1010) v phenol chuyn mu t vng (dng axit) sang (dng baz) khong pH = 6,4 8,0. 64Th nghim 3. S to thnh phc cht [Cu(NH3)4]2+ v s phn hy phc cht ny bng axitI. Mc ch th nghim Nghin cu s to thnh phc cht [Cu(NH3)4]2+ v s phn hy phc cht bi axit Rn luyn k nng: nh git ha cht lng bng cng t ht v quan st II. C s l thuytTrong dung dch nc Cu2+ c mu xanh lc. Dung dch c phn ng axit:Cu2+ + H2O CuOH+ + H+pH ca dung dch Cu2+ (102 M) vo khong 5Phc cht ca Cu2+ vi NH3 : Cu2+ + NH3 Cu(NH3)2+lg1 = 3,49Cu2+ + 2NH3 Cu(NH3)+ 22 lg2 = 7,33Cu2+ + 3NH3 Cu(NH3)+ 23 lg3= 10,06Cu2+ + 4NH3 Cu(NH3)+ 24 lg4= 12,03c mu xanh m, thng dng pht hin ra Cu2+ khi nng khng qu b. Tuy vy, cn ch rng bn ca phc cht khng ln nn d b phn hy di tc dng ca cc axit mnh.Cu(NH3)+ 24 + 4H+ Cu2+ + 4NH+4 lgK = 25 III. Dng c, ha cht th nghimDNG C HA CHT ng nghim, cp ng nghim ng ht nh git. Dung dch HCl 1M; (R34/37-S26/36/45) Dung dch NH3 c; (R10/23/34-S1/2/16/36/37 /39/45) Dung dch CuSO4 2M (R22/36/37/38 S26)..IV. Cc bc tin hnh th nghim65a) Ly khong 10ml dung dch CuSO4 2M vo ng nghim, nh t t n d dung dch NH3 vo ng nghim . Quan st hin tng xy ra.b) Thm tip t t dung dch HCl vo ng nghim. Quan st hin tng xy ra.V. Mt s lu th nghim thc hin thnh cng Khi nh dung dch hay thm dung dch cn ht sc t t tng git, va thc hin va quan st Tin hnh t ng nghim trn nn giy trng so snh mu r hnVI. Phn tch kt qu th nghim v Bo co a) Khi nh dung dch NH3 vo dung dch CuSO4 2M c hin tng g? Vit phng trnh ha hc? Khi d NH3 hin tng thay i nh th no? Vit phng trnh ha hc?b) Khi thm tip dung dch axit HCl, kt ta c xut hin tr li khng? Vit phng trnh ha hc gii thch?VII. Cu hi kim tra v m rng1) Trong qu trnh TN c s to thnh cc phc Cu(NH3)+ 23, Cu(NH3)+ 22 v Cu(NH3)2+ khng? V sao?2) Nu tip tc cho d dung dch HCl th hin tng xy ra th no?3) Thm NaOH d vo dung dch CuSO4, thm tip cho n d dung dch NH4NO3 th c hin tng g xy ra? Vit cc PTHH gii thch.4) Nu cc bc tin hnh xc nhn s c mt ca cc ion Cu2+, Cd2+ v Ni2+ trong cng mt dung dch.66Th nghim 4. S to thnh kt ta AgCl (t dung dch AgNO3 v dung dch HCl). S ha tan kt ta AgCl bng dung dch NH3I. Mc ch th nghim Nghin cu s to thnh kt ta AgCl v s ha tan kt ta bi NH3. Rn luyn k nng: nh git ha cht lng bng ng ht nh git, lc dung dch v quan st II. C s l thuyt* Ion Cl tc dng c vi ion Ag+ to thnh kt ta trng AgCl tan t trong HCl to thnh phc AgCl2.Ag+ + Cl AgClAgCl+ Cl AgCl2lgK = 5Khi pha long dung dch bng nc th nng ion Cl gim nn li xut hin kt ta AgCl (c)* Kt ta AgCl tan trong dung dch NH3 do to thnh phc amin Ag(NH3)2Cl. AgCl Ag+ +CllgK = 10Ag+ + 2NH3 Ag(NH3)+2 lgK =7,24AgCl+2NH3 Ag(NH3)+2 +CllgK = 2,76* Khi axit ha dung dch bng HNO3 th c kt ta AgCl xut hin tr li.* Kt ta AgCl cn c th tan trong dung dch (NH4)2CO3 v hn hp m (AgNO3 0,01M; NH3 0,25M; KNO3 0,25M hoc HNO3) III. Dng c, ha cht th nghimDNG C HA CHT ng nghim, cp ng nghim ng ht nh git My quay li tm hoc phu lc Giy lc . Dung dch HCl 2M;(R34/37-S26/36/45) Dung dch NH3 c; (R10/23/34-S1/2/16/36/37 /39/45) Dung dch AgNO3 2M (R34 S1/2/22/ 26/45)..67IV. Cc bc tin hnh th nghima) Ly khong 10ml dung dch AgNO3 2M vo ng nghim, nh t t dung dch HCl 2M vo ng nghim . Quan st hin tng xy ra.b) Pha long hn hp bng nc ri li tm hoc lc ly kt tab) Thm tip t t dung dch NH3 vo kt ta. Quan st hin tng xy ra.V. Mt s lu th nghim thc hin thnh cng Khi nh dung dch hay thm dung dch cn ht sc t t tng git, va thc hin va quan st Tin hnh t ng nghim trn nn giy trng so snh mu r hnVI. Phn tch kt qu th nghim v Bo co a) Khi nh dung dch HCl d vo dung dch AgNO3 c hin tng g? Vit phng trnh ha hc? Khi pha long hn hp hin tng c g khc khng? Vit phng trnh ha hc?b) Sau khi lc ly kt ta v thm dung dch NH3 d vo kt ta, hin tng thay i th no? Vit phng trnh ha hc gii thch?VII. Cu hi kim tra v m rng1) Hy nu cc k nng c bn khi s dng my quay li tm hoc lc dung dch qua phu lc?2) Ly 2 git dung dch NaCl, thm 2 git dung dch AgNO3, li tm ly kt ta chia lm 3 phn. Thm vo mi phn 2 git cc dung dch: NH3 2M; (NH4)2CO3 2M v hn hp m (AgNO3 0,01M; NH3 0,25M; KNO3 0,25M hoc HNO3). Li tm ly dung dch nc trong, ri thm 2 git dung dch HNO3 2M. So snh kt ta thu c trong 3 trng hp trn. Kt lun3) Ly 1 git dung dch NaCl thm vo 1 git hn hp m ni trn. Quan st hin tng. Thm tip 1 git HNO3. Quan st v gii thch. 68Bi 4. NGHIN CU TNH CHT HA HC CA ANDEHIT-XETON, AXIT CACBOXYLICTh nghim 1: Phn ng oxi ha fomandehit bng thuc th I. Mc ch th nghimNghin cu cc th nghim oxi ha nhm CH=O bng mt s cht oxi ha chng minh tnh kh ca cc anehit, qua bit cch phn bit andehit vi cc dn xut khc ca hidrocacbon. Bit mt s thuc th ha hc Rn cc k nng th nghim: Ty ra ng nghim, thm cht lng vo cht lng, nh cht lng bng ng ht nh git vo cht lng theo thnh ng nghim, un nng cht lng, quan st.II. C s l thuyt:1. Phn ng oxi ha andehit bng thuc th Tollens (phn ng trng bc)Amoniac to vi ion Ag+phc cht tan trong nc. Anehit kh c Ag+ phc cht thnh Ag kim loi : AgNO3+3NH3+H2O [Ag(NH3)2]OH+NH4NO3 (phc cht tan)RCH=O+2[Ag(NH3)2]OHR-COONH4 + 2Ag + 3NH3+H2O Phn ng trng bc c dng nhn bit nhm chc andehit v c ng dng trng gng, trng rut phch.2. Ngoi thuc th Tollens c th dng mt s thuc th khc nh:a) Thuc th Fehling: c mu xanh l phc ca Cu2+ vi ion tactrat to bi hn hp 2 dung dch ng (II) sunfat v dung dch kim ca mui seignett (mui kali natri tartrat: NaOOC CH CH COOK||OH OH.4H2O hay C4H4O6NaK.4H2O). Trong phn ng, Cu2+ oxi ha nhm CH=O thnh COONa; COOK, ng thi 69b kh thnh Cu+ (to kt ta gch Cu2O).Thuc th fehling dng nhn bit cc hp cht c nhm chc andehit. 2KNa[Cu(C4H4O6)2] + OH + RCHO + H2O Cu2O+ RCOO + 2H2C4H4O6 + 2KNaC4H4O6b) Thuc th Benedict: c mu xanh l phc ca Cu2+ vi ion xitrat to bi hn hp 2 dung dch ng(II)sunfat v dung dch kimca muixitrat COOH | HOOC2CHC 2CH COOH |OH. Trongphnng, Cu2+oxi hanhm CH=O thnhCOONa;COOK, ngthi b khthnhCu+(tokt tagch Cu2O). Thucthbenedictdngnhnbit andehit vccngkh. Trong y hc, thuc th benedict cn dng kim tra lng ng gluoz trong mu (nhm xc nh mc ca bnh tiu ng)III. Dng c, ha cht th nghimDNG C HA CHT ng nghim, kp g ng ht nh git n cn, Cc thy tinh 100 ml Ni cch thy.... Dung dch NaOH 10%;(R35-S1/2/26/37 /39/45) Dung dch NH3 c; (R10/23/34-S1/2/16/36/37 /39/45) Dung dch AgNO3 2M (R34 S1/2/22/ 26/45). Dung dch HCHO 40% (R10/35-S1/2/23/ 26/45) Thuc th fehling, thuc th benedict...IV. Cc bc tin hnh th nghimIV.1. Vi thuc th TollensRa sch ng nghim bng cch cho vo ng nghim 2ml dung dch NaOH 10% un si, b dung dch kim v trng ra vi ln bng nc sch.70Cho vo ng nghim sch 1ml dung dch AgNO33%, cho tip 1ml dung dch NaOH 10%, xut hin kt ta, cho tip dung dch NH3 5% vo hn hp phn ng cho ti khi kt ta mi to thnh tan ht. Tip tc cho vo hn hp phn ng mt vi git kim NaOH 10%. Rt khong 1ml dung dch fomanlin 40% vo hn hp phn ng. Ch rt nh theo thnh ng nghim. un nh hn hp vi pht trn n cn (khng cho hn hp phn ng si), duy tr nhit 35oC trong thi gian 2,0 - 3,0 pht. Quan st th nghim. IV.2. Vi thuc th Fehling:Cchp hathucthFehling: hatan 0,4gamCuSO4.5H2Otrong 10ml nc ct (nu dung dch c th cn lc) c dung dch A. Ha tan 0,2 gam C4H4O6NaK.4H2O v 1,5 gam NaOH trong 10ml nc ct c dung dch B. Thuc th Fehling (ch pha ngay trc khi s dng hn ch s to thnh kt ta Cu(OH)2): trn 1 th tch dung dch A v 1 th tch dung dch B, lc u, thu c dung dch thuc th Fehling trong, xanh bic.S dng thuc th Fehling lm th nghim tng t thuc th Tollens.IV.3. Vi thuc th Benedict:Cch p ha thuc th Benedict: ha tan 17,3g natri citrat trong 70ml nc ct un si, thm 10g Na2CO3 khan, lm lnh, thm t t 10ml dung dch CuSO4 17,3%, thm nc n 100ml, dung dch benedict c mu xanh dng.S dng thuc th benedict lm th nghim tng t thuc th Tollens.V. Mt s lu th nghim thc hin thnh cngNung nghim khngc ratht sch thkt taAg sinh ranhanh, khng to ra gng m to mt mng en. Khi un nng hn hp phn ng khng nn lc ng nghim m yn cho lp Ag to ra t t mi thu c gng p. Th nghim xong, ra ng nghim bng dung dch HNO3 long, cc cht vo cc thu hi sn phm. C th thay vic un nng nh hn hp bng cch t ng nghim vo ni cch thy ang si hoc ngm ng nghim trong cc nc si.Cn cho d kim do phn ng oxi ha andehit xy ra trong mi trng kim7172VI. Phn tch kt qu th nghim v Bo co Cho dung dch NaOH vo ng nghim ng AgNO3 thy c hin tng g? Thm tip dung dch NH3 hin tng c g khc khng? Vit phng trnh ha hc. Thm formalin vo hn hp c thay i g cha? Khi un nng nh hin tng xy ra nh th no? Vit phng trnh ha hc gii thch. Khi s dng thuc th Fehling v benedict lm th nghim tng t thuc th Tollens th hin tng xy ra nh th no? Vit cc phng trnh ha hc.VII. Cu hi kim tra v m rng1) Mun cho phn ng trng bc thu c kt qu tt cn phi lm th no?2) Trng hp khng c n cn un nng th lm th no phn ng trng bc xy ra?3) i khi kt thc th nghim phn ng trng bc, trong ng nghim xut hin mu en, hy gii thch hin tng ny?4) i khi th nghim phn ng trng bc khng thnh cng, hy cho bit nguyn nhn?5) M t thao tc khi un nng nh ng nghim phn ng xy ra nhanh hn.6) ly ha cht lng t l ng ha cht cho vo ng nghim, ngi ta s dng cch no trong cc cch sau :A. Dng ng nh git ht ha cht t l ng sang ng nghim. B. trc tip l ng ha cht cho vo ng nghim. C. t p ming ng nghim va kht vo ming l ng ha cht, sau dc ngc l ng ha cht ha cht t t chy sang ng nghim .D. Dng mung mc cht lng t l sang ng nghim73Th nghim 2:Tnh cht ha hc c trng ca axetonI. Mc ch th nghim Nghin cu th nghim phn ng iodofom ca axeton v phn ng gia axeton vi 2,4- initrophenylhirazin, chng minh kh nng phn ng th nguyn t O trong nhm C=O bng nguyn t N (phn ng ngng t) v kh nng th nguyn t H trong gc hirocacbon ca xeton.Bit cchnhnranhm>C=Ovnhm CHOHCH3bngccphnngc trng. Rn cc k nng th nghim: nh cht lng bng ng ht nh git vo cht lng theo thnh ng nghim, un nng cht lng, quan st.II. C s l thuyt1. Trong phn t xeton R2CH C3CH ||O , nguyn t H ca gc hidrocacbon c hot ha bi nhm >C=O tr nn linh ng hn d b thay th, ng thi hp cht >C=O c kh nng chuyn thnh dng enol theo mt cn bng:

|CC | ||O C =C OH | | (dng xeton) (dng enol)Khi ,nguynthirov trivi nhm>C=O trongphntxeton (anehit cng vy) d b th bi clo, brom hoc iot. Th d :

3CHC3CH ||O +X2 Hhoc OH+3CHC2CH X ||O + HX (X l Cl, Br, I)Trongtrnghpdngdhalogenvthchinphnngtrongmi trng kim:3CHCR ||O 3CXCR ||O (R : hiro, ankyl, aryl...) 74dn xut 3CXCR ||O b kim phn ct ngay thnh CHX3 (halofom) v RCOONa. Th d : cho iot v NaOH tc dng vi axeton :3CHC3CH ||O +I2 +3NaOH 3CHC3CI ||O + 3NaI + 3H2O 3CHC3CI ||O +3NaOH CHI3 (mu vng) + CH3COONaPhn ng ny c gi l phn ng ioofom dng nhn bit nhm CH3CO- trongphntxetonhocanehit hocnhmCH3-CHOH- trongphnt ancol (v trong iu kin ca phn ng ioofom, nhm CH3-CHOH- b oxi hathnhCH3-CO-). Ngoi raphnngnycncdngiuch CHI3, CHBr3 v CHCl3 t axeton hoc t etanol.2. Hp cht xeton khng ch c phn ng th nguyn t H gc hirocacbon m cn phn ng th nguyn t O trong nhm >C=O bng nguyn t N to nn lin kt cacbon nit (phn ng ngng t vi dn xut ca amoniac RNH2)RC =O | R + H2N-R' RC =N R' | R + H2OS phn ng: +>C=O +H2N Ycng 1 1 1 1 ] OH\ /C/\ NHY H Otch2>C = N YTh d: C ch phn ng gia 2,4 - dinitrophenylhydrazine v aldehyt hoc xeton c biu din di y: 75

Phnngtothnhphenylhirazon, cbit l2,4initrophenylhirazin c dng nhn ra xeton (v anehit) v 2,4-initro phenylhirazon l nhng cht c mu hoc da cam (nu l xeton thm),c mu vng (nu l xeton khng thm) v rt t tan trong cc dung mi thng thng.III. Dng c, ha cht th nghimDNG C HA CHT ng nghim, kp g ng ht nh git n cn hoc cc nc nng.... Dung dch NaOH 10%;(R35-S1/2/26/37 /39/45) Axeton; (R11 S9/16/23/33) Iot (tinh th) (R21/30/35/-S/29/35/41) 2,4-initro phenylhyrazine (DNPH) (R 1-11-22, S 35)....76IV. Cc bc tin hnh th nghimIV.1. Phn ng iodofom ca axetonCho vo ng nghim sch 10 ml axeton, th vo ng nghim 2,0 gam Iot, lc u cho ti khiIot bt u tan trong axeton. Sau thm t t tng git dung dch 10% NaOH v tip tc lc ng nghim trn ln cc cht, ri gi ng nghim nhit phng 20 pht. Nu vn khng c g xy ra, lm nng ng nghim nh cc th nghim ng nc nng, duy tr nhit 35oC trong thi gian 5 pht. Quan st hin tng.IV.2. Phn ng ca axeton vi 2,4- initro phenylhirazine (DNPH)iuchthucth2,4-initrophenylhyrazinbngcchhotan3,0gam 2,4-initrophenylhyrazin vo 15 mlaxit sunfuric c v thm vo dung dch ny 20 ml nc vi 70 ml etanol 95%, trong iu kin khuy trn tt hn hp. Ho tan 100 mg axetontrong 2 mletanol 95%, ri 2 mlthuc th 2,4-initro phenylhyrazin vo dung dch ny. Lc mnh hn hp. V. Mt s lu th nghim thc hin thnh cng Cn s dng ng th t cc ha cht phn ng Trong c hai th nghim phi lc u tay v duy tr nhit cn thit Nu kt ta khng xut hin ngay, th yn dung dch 15 phtVI. Phn tch kt qu th nghim v Bo coIV.1. Phn ng iodofom ca axeton+ Iot tan dn trong axeton lm dung dch c mu g?+ Sau khi thm dung dch NaOH, phn ng bt u xy ra nhanh hn, khi mu sc dung dch thay i cha? Vit phng trnh ha hc.77+Khi lm nng hn hp, hin tng xy ra nh th no? Vit phng trnh ha hc gii thch?+ Nu kt lun v ng dng ca phn ng ny? IV.2. Phn ng ca axeton vi 2,4- initro phenylhirazine (DNPH)+ Thuc th iu ch c c mu g?+ Sau khi trn vi dung dch axeton trong etanol, phn ng bt u xy ra, Vit phng trnh ha hc ca phn ng?+ Sau 15 pht, gi yn hn hp, hin tng xy ra nh th no?+ Nu kt lun v vic s dng DNPH?VII. Cu hi kim tra v m rng1) Cho 4 cht : axeton ; axetanehit, propionanehit v ancol isopropylic.Hy phn bit cc cht bng phng php ha hc.2)NuchoccchtlngHCOOH, CH3COOH, CH3CH2CHO, CH3COCH3v CH2=CHCOOH, lm th no phn bit chng bng phng php ha hc ?3) Trong 5 l khng nhn cha ring r 5 hp cht thm l: C6H5COCH2CH3; C6H5COOH; C6H5COCH3; C6H5CHOHCH3; C6H5CH=O. Da vo cc kt qu th nghim sau cho bit k hiu ca mi cht: Cho vo mi cht mt git hn hp kali bicromat + axit sunfuric v lc u, sau vi pht thy mu ca A v C bin i t da cam thnh xanh lc; Cho vo mi cht mt t dung dch NaOH long th ch ring B tan c; Khi cho tc dng vi iot trong dung dch kim A v E to ra kt ta vng; Lc vi 2,4-initrophenylhyrazin thy C, D, E u phn ng to kt ta mu da cam. 4)2,4-initrophenylhyrazinthngmithnglbttciuchbi phn ng ca hirazin sunfat (N2H4.H2SO4) vi 2,4 initroclorobenzen trong dung mi CH3COOK. Hy vit phng trnh ha hc ca phn ng ny78Th nghim 3: Phn ng este haI. Mc ch th nghim Nghin cu th nghim phn ng ha este gia axit axetic vi ancol etylic chng minh phn ng hu c thng xy ra rt chm iu kin thng v l phn ng thun nghch. Bit cch s dng cc bin php dch chuyn cn bng ca phn ng v lm tng hiu sut phn ng Rn cc k nng th nghim: Ty ra ng nghim, thm cht lng vo cht lng, nh cht lng bng ng ht nh git vo cht lng theo thnh ng nghim, un nng cht lng, quan st.II. C s l thuyt:Phn ng ca ancol vi axitcacboxylic, caxit vcmnhlmxctc (thng l H2SO4 m c) thu c este c gi l phn ng este ha3||CH C OH + 2 5H OC H 3 2 5||CH C O C H + 2H OAxit axetic Ancol etylic Etyl axetat NcPhn ng esteha lrt chmiukinthngvlphn ng thun nghch. Nu ta trn mt mol CH3COOH vi mt mol C2H5OH th dn dn s sinh ra CH3COOC2H5v H2O, ng thi lng CH3COOH v C2H5OH s gim i. Sau mt thi gian di (khong mt nm nhit phng) hn hp c thnh phn khng i, gm 1/3 mol axit axetic, 1/3 mol ancol etylic, 2/3 mol este v 2/3 mol nc. Ta gi l trng thi cn bng ha hc. Hng s cn bng Kcb ca phn ng c tnh nh sau :3 2 5 2cb3 2 5[CH COOC H ][H O] 2/3.2/3K 4[CH COOH][C H OH] 1/3.1/3 Munchophnngmautti trngthi cnbng, tcltngtc phn ng, ngi ta dng cht xc tc axit (H2SO4, HCl khan v.v...) v un nng. Mun chuyn dch cn bng v pha to ra este ta c th tng nng ca 79OOmt trong hai cht u (ancol hoc axit cacboxylic) v chng ct dn este ra khi mi trng phn ng.C ch ca phn ng este ha gm hai giai on c bn l cng nucleophin ancol vo nhm cacboxyl c hot ng ha bng H+ v tch nc t sn phm cng c este dng proton ha ; dng ny b tch proton s cho este. Th d : nng cao hiu sut phn ng (cn bng dch chuyn theo chiu thun, to thnh este) c th ly d mt trong hai cht tham gia phn ng hoc lm gim nng cc cht sn phm.Axit H2SO4m c va lm xc tc, va c tc dng ht nc, do gp phn lm tng hiu sut este.III. Dng c, ha cht th nghimDNG C HA CHT ng nghim, gi ng nghim, Nt cao su c l cm dn kh hnh thc th n cn. Cc thy tinh 100 ml Bng, bt... CH3COOH 20%; (R36/37/38-S23/26/ 45) Etanol; (R11-S7/16) H2SO4 c 96%; (R21/22/27/34/35/41/-S1/2/5/7/18/23/25/27/29)....IV. Cc bc tin hnh th nghimRt vo ng nghim 2,5 ml C2H5OH 960, rt tip vo 2,5ml axit axetic, cho thm vo hn hp phn ng 1ml H2SO4 m c, lc nh hn hp phn ng cho 80cc cht trn u vo nhau; thm vo hn hp phn ng vi vin bt. y ng nghim bng nt cao su c cm ng dn kh hnh thc th, a u ng dn kh vo ng nghim c cha sn ng nghim nc lnh, u ng dn kh gn st ti y ca ng nghim ng nc, ton b ng nghim ny c ngm trong cc ng nc . un nng ton b hn hp phn ng. Ch un ui t y ng nghim ln pha ming ng nghim este sinh ra bay sang ng nghim thu sn phm c nhng trong cc nc lnh; este thu c c mi thm c trng.V. Mt s lu th nghim thc hin thnh cngKhi ngng th nghim,tho nt ng dn kh,tt n cn, b ng dn kh khi ng thu sn phm.Thsnphmbngcch: Lyngntayci bt mingngnghimcha etylaxetat, dc ngc ng, etylaxetat tip xc vi ngn tay khong pht, h m ngn tay nc phun ra thnh tia. VI. Phn tch kt qu th nghim v Bo coCH3COOH + C2H5OH + ot H ,CH3COOC2H5 + H2OSn phm thu c l etylaxetat l cht lng, d bay hi, c mi thm c trng.Este etylaxetat sinh ra bay sang ng nghim thu sn phm c nhng trong cc nc lnh, este chuyn sang dng lng khng tan trong nc. Cht lng thu c gm nc ( pha di) v etylaxetat khng tan, nh hn nc ( pha trn) c mi thm c.VII. Cu hi kim tra v m rng1) Hy cho bit vai tr ca H2SO4 m c trong qu trnh th nghim. Mun to ra nhiu sn phm este cn phi ch nhng vn g?2) Cho C6H5-CO-Z (Z = OH, Cl, OOC6H5) tc dng vi C2H5OH.a- Vit cc phng trnh phn ng.b- Phn ng no xy ra nhanh nht ? Ti sao ?c- Phn ng no xy ra chm nht ? Nu iu kin phn ng v c ch ca phn ng .813) Hy nu cch phn bit cc dung dch axit axetic, anehit axetic v etanol cha trong ba l khng dn nhn.82Th nghim 4:Phn ng iu ch CH3COOH t CH3COONaI. Mc ch th nghim Nghin cu th nghim phn ng gia axit sunfuric m c vi Natri axetat iu ch axit axetic, chng minh axit axetic l mt axit yu. Rn cc k nng th nghim: Lp dng c theo b trn gi th nghim, thm cht lngvochtrn, mkhaphuchochtlngchyxungbnhcu, un nng cht lng, x l cht thi, quan st.II. C s l thuytTrong dung dch nc, axit cacboxylic phn li theo mt cn bng :( ) ( )3 2 3 3CH COOH +H O CH COO H O + +Ka = [ ]RC H ORCOOH + 11 ] ]3 l hng s ion ha ca axit. Ka cng ln, hoc pKa = -lgKa cng nh, lc axit cng mnh.Tuy nhin, axit cacboxylic ni chung ch l nhng axit yu (Ka = 1,8 105); cho nn cc axit mnh nh H2SO4, HCl... c th y chng ra khi mui tng ng. Th d :un nng3 2 4 3 2 42CH COONa H SO 2CH COOH Na SO + +Phn ng ny dng nhn ra mui axetat kim loi v iu ch axit axetic trong phng th nghim.III. Dng c, ha cht th nghimDNG C HA CHT Bnh cu c nhnh, gi ng nghim, Bnh tam gic 100 ml Phu brom (phu hnh qu l) Nt cao su c l cm dn kh hnh thc th n cn. Cc thy tinh 100 ml Bng Phu thy tinh nh .... CH3COONa khan; (S22/24/25) H2SO4 c 96%; (R21/22/27/34/35/41/-S1/2/5/7/18/23/25/27/29/) NaOH 0,01M; (R35-S1/2/26/37/ 39/45) Nc...83IV. Cc bc tin hnh th nghimM kha phu brom cho axit H2SO4m c nh t t xung bnh cu c nhnh ng khong3 gam CH3COONa khan,un nh.ng dnkh cmvo bnh tam gic c ng nc thu CH3COOH. Ly ming bng tm dung dch NaOH long y trn ming bnh tam gic. Th kh xem y bnh cha bng cch mu giy qu tm m ming bnh tam gic nu qu chuyn mu chng t dung dch axit axetic bo ha. Nhc ng dn kh ra, y np bnh tam gic li ng thi cm tip vo bnh thu axit axetic tip theo.Khi ngng un, tho ng dn kh ra, lp phu thy tinh nh chm vo bng c tm dung dch NaOH long trong cc kh axit axetic d. V. Mt s lu th nghim thc hin thnh cng Ch H2SO4 m c, CH3COONa phi kh, h thng th nghim phi kn. Sn phm l hi axit nn phi tun th nghim ngt quy tc an ton VI. Phn tch kt qu th nghim v Bo co Khi m kha phu brom cho axit H2SO4 m c nh t t xung bnh cu cnhnhngCH3COONakhan,unnhth chin tngg? Vitphng trnh ha hc ca phn ng Quan st bnh tam gic c nc v ming bng y trn ming bnh thy c hin tng g? Gii thch. VII. Cu hi kim tra v m rng1) V sao phi y ming bng tm dung dch NaOH trn ming bnh tam gic?2) Khi ngng un c nn tho ngay ng dn kh ra khi nhnh ca bnh cu khng?3) Hy ngh mt thc nghim khc chng t axit axetic l axit yu.4) Trong th nghim trn ti sao li dng H2SO4 m c, c th dng axit khc c khng?84Bi 5.TNH CHT CA MT S CHT HU CTh nghim 1: Xc nh ch s axit ca cht bo I. Mc ch th nghimNghin cu th nghim phn ng gia cht bo vi dung dch NaOH, xc nh lng NaOH trung ha 1,0 gam cht bo suy ra ch s axit ca cht bo. Rn cc k nng th nghim: Cn,s dng pipet,nh git cht lng vo cht lng, quan st, ghi chp, tnh ton.II. C s l thuytTrong cc cht bo thng c cha mt lng axit t do. nh gi lng axit botdoctrongcht bongi tadngch saxit. Ch saxit ls miligam KOH trung ha axit bo t do c trong 1 gam cht bo. Trong cc th nghim, thng dng NaOH trung ha axit, t lng NaOH s xc nh c ch s axit.III. Dng c, ha cht th nghimDNG C HA CHT Bnh tam gic 250 ml Cn in t hin s. Pipet my Cht bo lng; NaOH 30%; (R35-S1/2/26/37/ 39/45) Cht ch th phenolphtaleinIV. Cc bc tin hnh th nghimCn 2,0 gam cht bo lng cho vo bnh tam gic c cha sn mt vi git phenolphtalein. Dng pipet my nh tng git dung dch NaOH 30% vo bnh tam gic. Va nh dung dch va lc hn hp phn ng n khi hn hp phn ng bt u xut hin mu hng th dng li. Xc nh th tch dung dch NaOH 30%.V. Mt s lu th nghim thc hin thnh cng Nh dung dch NaOH tng git v lc km theo di mu ca cht ch th Ch khi c th tch dung dch NaOH.VI. Phn tch kt qu th nghim v Bo co85Khi cho NaOH vo cht bo lng, NaOH s phn ng vi axit t doNaOH + RCOOH RCOONa + H2OKhi ht axit, mt git NaOH d s lm dung dch c cha phenolphthalein chuyn mu hng.Khi hn hp phn ng bt u xut hin mu hng th dng li. Xc nh th tch dung dch NaOH 30%. Tnh s mol NaOH,s mol KOH v da vo khi nim ch s axit tnh ton xc nh ch s axit.VII. Cu hi kim tra v m rng1) Cht bo c cc loi ch s: axit, x phng ha, este, iot, peroxitHy gii thch mi loi ch s ny?2) C mt cht bo gi s thuc loi triolein.a) Xc nh ch s x phng ha v ch s iot ca cht bo b) Tnh khi lng cht bo cn iu ch 5,880 kg glixerol, nu hiu sut t 85%.c) Tnh khi lng tristearin sn xut c t 1 tn cht bo , bit hiu sut l 80%.3) x phng ha 10 kg cht bo c ch s axit bng 7 ngi ta un n vi dung dch cha 1,420 kg NaOH.Sau phn ng, trung ha hn hp cn dng 0,5 lt HCl 1M. Tnh khi lng x phng thu c, gi s hiu sut l 100%.Th nghim 2:Phn ng ca glucoz vi thuc th Tolen, Felinh, Benedict v nc bromI. Mc ch th nghimNghin cu th nghim phn ng gia glucoz vi thuc th tollens, thuc th Fehling, thuc th Benedict v nc brom. Bit cch nhn ra glucoz v phn bit glucoz vi fructoz v cc cacbohidrat khc86 Rn cc k nng th nghim: Ty ra ng nghim, thm cht lng vo cht lng, nh cht lng bng ng ht nh git vo cht lng theo thnh ng nghim, un nng cht lng, quan st.II. C s l thuytV trong phn t glucoz c cha nhm chc CHO nn c kh nng phn ng vi thuc th Tollens, Fehling v Benedict (ging nh andehit)Phn ng oxi ha glucoz bng thuc th Tollens (AgNO3 trong dung dch NH3) hoc Fehling (phc cht ca Cu2+vi mui Natri kali tactrat trong dung dchNaOH NaOOC CH CH COOK||OH OH)vBenedict (phccaCu2+vi ion xitrat to bi hn hp 2 dung dch ng (II) sunfat v dung dch kim ca mui xitrat COOH | HOOC2CHC 2CH COOH |OH) xy ra trong mi trng kim nn khng phnbit cglucozvfructoz(trongmi trngkimfructozchuyn thnh glucoz:Fructoz Glucoz). (Xem thm Bi 4 th nghim 1 trang 68) phn bit glucoz v fructoz phi dng dung dch brom:CH2OH(CHOH)4CHO + Br2+ H2OCH2OH(CHOH)4COOH + 2HBrIII. Dng c, ha cht th nghimDNG C HA CHT ng nghim, kp g ng ht nh git n cn, Cc thy tinh 100 ml... Dung dch NaOH 10%;(R35-S1/2/26/37 /39/45) Dung dch NH3 c; (R10/23/34-S1/2/16/36/37 /39/45) Dung dch AgNO3 2M (R34 S1/2/ 26/45). Dung dch glucoz 1% (R10/35-S1/2/23/ 26/ 45)87 Dung dch nc brom 2M (R21/22/27/34/35 -S18/23/25/27/29/) Dung dch bo ha CuSO4 (R22/36/37/38 S26) Bt Na2CO3, Bt natri citrat HOOCCH2C(OH)(COOH)CH2COONa Bt C4H4O6NaK.4H2O Nc ct ....IV. Cc bc tin hnh th nghimIV.1. Nhn bit glucoz bng thuc th TollensRa sch ng nghim bng cch cho vo ng nghim 2ml dung dch NaOH 10% un si, b dung dch kim v trng ra vi ln bng nc sch.Cho 1ml dung dch AgNO3 3% vo ng nghim sch s 1, cho tip 1ml dung dch NaOH 10%, kt ta xut hin, cho tip dung dch NH3 5% vo hn hp phn ng cho ti khi kt ta mi to thnh tan ht. Tip tc cho vo hn hp phn ng mt vi git kim NaOH 10%. Rt thm 2ml dung dch glucoz 1% vo hn hp phn ng.Ch rt nh theo thnh ng nghim.un nng hn hp vi pht trong ni nc nng 60oC - 70oC

(khng cho hn hp phn ng si). Quan st th nghim. IV.2. Nhn bit glucoz bng thuc th Fehling hoc thuc th BenedictPha thuc th Fehling v thuc th Benedict nh hng dn Bi 4 th nghim 1 trang 69.Cho 2ml dung dch glucoz 1% vo ng nghim, thm tip 1ml thuc th Fehling (hoc thuc th Benedict).Lc u ng nghim, un n khi bt u si, quan st hin tng. Ch : Phn ng vi thuc th Benedict rt c trng v nhy vi ng kh hn phn ng vi thuc th FehlingIV.3. Nhn bit glucoz bng dung dch nc bromRt 2ml dung dch brom vo ng nghim sch s 3, thm tip vi git dung dch glucoz 1%, lc mnh ng nghim. Quan st hin tng.88V. Mt s lu th nghim thc hin thnh cngNu ng nghim khng c ra tht sch th kt ta Ag sinh ra nhanh, khngtoragngmtomt mngen. Khi unnnghnhpphnng khng nn lc ng nghim m yn cho lp Ag to ra t t mi thu c gng p. Phn ng vi thuc th Benedict rt nhy, ch cn s dng glucose 0,1% l to kt ta Cu2O gch, tuy nhin kt ta ln vi dung dch mu xanh dng nn dung dch chuyn sang mu xanh m.+ Nu s dng glucose 1% th lng kt ta sinh ra ln, s nhn thy r kt ta Cu2O (ln vi mu xanh ca dung dch nn khng thy mu gch m chuyn sang nu, gn nh en). Th nghim xong, ra ng nghim bng dung dch HNO3 long, cc cht vo cc thu hi sn phm.VI. Phn tch kt qu th nghim v Bo coVI.1. Nhn bit glucoz bng thuc th Tollens+ ng nghim xut hin kt ta? Mu kt ta l mu g? + Theo l thuyt th mu kt ta l mu g? Ti sao thc t mu kt ta li khc? Gii thch kt qu thu c v vit phng trnh ha hc. Kt lun rt ra l g?VI.2. Nhn bit glucoz bng thuc th Fehling hoc thuc th Benedict+ Dung dch chuyn mu nh th no? Nu s dng glucose 1% th c th thy kt ta mu g? Gii thch kt qu thu c v vit phng trnh ha hc. Kt lun rt ra l g?VI.3. Nhn bit glucoz bng dung dch nc brom+ Dung dch brom chuyn mu nh th no? Gii thch kt qu thu c v vit phng trnh ha hc. Nu kt lun v ng dng ca thuc th ny?89VII. Cu hi kim tra v m rng1) Phn ng nhn ra cc nhm hydroxyl v nhm cacbonyl trong phn t glucoz u dng Cu(OH)2. Hy phn bit iu kin phn ng2) Bng phn ng ho hc hy phn bit cc cht trong mi dy sau :a) Glucoz ; fomanehit.b) Glucoz ; fomanehit ; glixerol ;c) Glucoz ; fructoz ; axetanehit.d) Glucoz ; axetanehit ; glixerol ; etanol.3) Cho mt thuc th duy nht l X ; vi thuc th c th phn bit c cc dung dch trong mi trng hp sau :a) Saccaroz v glucoz ;b) Saccaroz v mantoz ;c) Saccaroz, mantoz v axetanehit.X l cht g ? Cch phn bit cc dung dch nu trn nh th no ?Th nghim 3: S thy phn ca tinh btI. Mc ch th nghim Nghin cu th nghim phn ng thy phn tinh bt, th phn ng kt thc bng thuc th dung dch I2 v th sn phm thy phn vi thuc th tollens, thuc th Fehling, suy ra thnh phn cu to nn tinh bt. Bit cch nhn ra tinh bt bng Iot v phn bit glucoz vi tinh bt. Rn cc k nng th nghim: Ty ra ng nghim, thm cht lng vo cht lng, nh cht lng bng ng ht nh git vo cht lng theo thnh ng nghim, un nng cht lng, quan st.II. C s l thuytTinh bt c phn t khi rt ln. Khi em thu phn n cng, tinh bt cho ta glucoz. Vy c th coi tinh bt l polime do nhiu mt xch glucoz lin kt 90vi nhau v c cng thc (C6H10O5)n, n = t 1000 n 6000. Thc cht tinh bt l mt hn hp ca hai loi polisaccarit l amiloz v amilopectin.Amiloz l polime c mch khng phn nhnh, Trong phn t amiloz cc mt xch -glucoz ni vi nhau bng lin kt-1,4-glicozit tc l lin kt C1 ca mt xch ny vi oxi C4 ca mt xch khc tng t nh phn t mantoz Phn t amilopectin cng do cc mt xch -glucoz ni vi nhau ch yu bnglinkt-1,4glicozit. Songamilopectincmchnhnh, chphn nhnh c thm lin kt-1,6-glicozit ni lin nguyn t C1 u ca on mch ny vi nguyn t oxi C6ca mt mt xch pha trong ca on mch khc :Dung dch h tinh bt khng c phn ng trng bc.Khi un nng dung dch h tinh bt trong mi trng axit, h tinh bt b thy phn hon ton cho glucoz(C6H10O5)n + nH2On C6H12O6CH2OH(CHOH)4CHO + 2[Ag(NH3)2]OH CH2OH(CHOH)4CONH4 + 2Ag+ 3NH3 + H2O91III. Dng c, ha cht th nghimDNG C HA CHT ng nghim, kp g ng ht nh git n cn, Cc thy tinh 100 ml Dung dch NaOH 10%;(R35-S1/2/26/37 /39/45) Dung dch NH3 c; (R10/23/34-S1/2/16/36/37/39/45) Dung dch AgNO3 2M (R34 S1/2/ 26/45). Dung dch h tinh bt Iot (tinh th) (R21/30/35/-S/29/35/41) Etanol (R11- S 7/16) Dung dch bo ha CuSO4 (R22/36/37/38 S26) Thuc th fehling, Thuc th benedict.IV. Cc bc tin hnh th nghimCch pha ch dung dch h tinh bt:Ly 3 gam tinh bt cho vo cc thy tinh 200ml, thm tip khong 100ml nc si, khuy u, thu c dung dch h tinh bt.Cho vo ng nghim khong 3ml dung dch h tinh bt, thm tip khong 4ml ncv 1ml dung dch H2SO4 (1:5). un si hn hp phn ng t 3-5 pht, khi uncndngathytinhkhuyuhnhpphnng. Saukhi un khong 3 pht, ly khong 0,5ml dung dch phn ng cho vo ng nghim khc, ngui, nh vi git dung dch I2 (pha trong cn). Nu dung dch chuyn mu xanh c ngha l h tinh bt cha thy phn ht. Tip tc un hn hp phn ng cho n khi ly dung dch trong ng nghim ang thy phn, em th vi dung dch I2 (pha trong cn) khng c mu xanh. Tinh bt b thy phn ht.Cch pha ch thuc th Tollens, Fehling, Benedict (xem Bi 4 Th nghim 1 trang 69)92 hn hp phn ng trong ng nghim ngui, trung ha axit d trong dung dch h tinh bt n mi trng kim d (th bng qu tm). Chia hn hp phn ng thnh 2 phn vo 2 ng nghim th sn phm. ng nghim 1 th phn ng vi thuc th Tollens. Quan st hin tngng nghim 2 th phn ng vi thuc th Fehling hoc Benedict. Quan st hin tngV. Mt s lu th nghim thc hin thnh cng Mun cho th nghim thnh cng cn phi un si k, khuy u hn hp phn ng. Phi trung ha axit H2SO4 d trong hn hp phn ng n mi trng kim d.VI. Phn tch kt qu th nghim v Bo coTinh bt t tan trong nc lnh, tan tt hn trong nc nng, do cn cho tinh bt vo nc v un si thu c h tinh btun h tinh bt trong mi trng axit thc hin phn ng thy phn, ngui hn hp phn ng, trung ha axit bng kim d do phn ng vi thuc th Tollens v Fehling xy ra trong mi trng kim.ng nghim 1: xut hin kt ta mu trng sng.ng nghim 2: xut hin kt ta mu gch.VII. Cu hi kim tra v m rng1) Hy gii thch v sao khi nh iot vo h tinh bt th xut hin mu c trng, nhng khi un nng mu c trng li bin mt?2) Trong th nghim trn, c cn thit phi th bng iot khng? V sao?3) Hy xut mt tin trnh th nghim khc xc nh c sn phm thy phn v phn bit c sn phm thy phn vi cht ban u?4) Tinh bt ng vt: Glicogen c cu trc gn vi amilopectin; l polime mch phn nhnh do cc mt xch -glucoz to nn bng cc lin kt-1,4- v -1,6-glicozit. Phn t glicogen khc vi amilopectin ch no?5) Nu phng php ha hc phn bit: tinh bt, glicogen, Saccaroz, glucoz v frutoz?93Th nghim 4: Mt s phn ng mu ca amino axit v proteinI. Mc ch th nghimNghin cu th nghim v phn ng mu ca aminoaxit v protein, t bit cch phn bit -aminoaxit vi cc loi aminoaxit khc. Bit cch phn bit Protein vi ipeptit.Rn cc k nng th nghim: thm cht lng vo cht lng, nh cht lng bng ng ht nh git vo cht lng theo thnh ng nghim, lc cht lng trong ng nghim, un nng cht lng, lm lnh cht lng, quan st.II. C s l thuyt1. Cc amino axit u c phn ng vi ninhirin (C9H6O4) cho sn phm c mu tmxanh (ring prolinchomuvng). Phnng nyrt nhy nncdng trong phn tch nh tnh v nh lng amino axit.OOOHOH++ R CH COOHNH2Ninhidrin Amino axitOONOOHR CH O + CO2+ 3H2OMu tm xanh2. Nhng Peptit c t hai nhm peptit tr ln v Protein c mt s phn ng mu c trng:a) Phn ng biure: tc dng vi CuSO4trong dung dch kim to ra phc cht mu xanh tm (phc to bi Cu2+ v hai nhm peptit)b) Phn ng xantoproteic: tc dng vi HNO3 c s to thnh hp cht mu vng do phn ng nitro ha vng benzen cc gc amino axit Phe, TyrIII. Dng c, ha cht th nghimDNG C HA CHT ng nghim, kp g ng ht nh git n cn, Cc thy tinh 100 ml Dung dch NaOH 30%;(R35-S1/2/26/37 /39 /45) Axit nitric HNO3 65% (R35 S23/26/36/ 45) Dung dch protit94.... Dung dch CuSO4 5% (R22/36/37/38 S26) Ninhyrin 0,5% trong axeton(C9H6O4); (R11/22/36/37/38 S9/16/26)...IV. Cc bc tin hnh th nghimIV.1.Cho vo ng nghim s 1 khong 2ml dung dch Glyxin (H2NCH2COOH), thm vo khong mt vi git thuc th Ninhyrin. Quan st s xut hin ca mu sc.IV.2.Cho vo ng nghim s 2 khong 2ml dung dch protein (lng trng trng), thmvokhong1ml dungdchNaOH30%vthmtipvi git CuSO4 5% (thuc th biure). Lc u hn hp phn ng. Quan st mu sc ca dung dch v gii thch.IV.3.Cho vo ng nghim s 3 khong 1ml dung dch protein (lng trng trng), sau thm vo ng nghim 0,5ml HNO3 c (d= 1,4g/ml). Lc u hn hp phn ng. Quan st mu sc ca dung dch v gii thch.V. Mt s lu th nghim thc hin thnh cng C th iu ch sn Cu(OH)2 trc lm thuc th, VI. Phn tch kt qu th nghim v Bo co ng nghim s 1: xut hin dung dch c mu tm xanh c trng tan trong nc

OOOHOH++R CH COOHNH2Ninhidrin Amino axitOOR CH O + CO2+ 3H2OOHH OOOHOH+NinhidrinOONOOH+ NH3Mu tm xanhOOOHOH ng nghim s 2: xut hin dung dch c mu xanh tm c trng l doCuSO4 + NaOH Cu(OH)2+ Na2SO495Cu(OH)2 phn ng vi hai nhm CO-NH trong protein cho sn phm mu xanh tm (ging mu ca phn ng gia Cu(OH)2 vi biure, gi l phn ng mu biure) ng nghim s 3: thu c kt ta mu vng l do nhm C6H4OH ca mt s gc amino axit trong protein phn ng vi HNO3cho hp cht mi mangnhm NO2 c mu vng, ng thi protein b ng t bi HNO3 to thnh kt ta. VII. Cu hi kim tra v m rng1) Khi thc hin phn ng mu biure c nn dng d CuSO4 khng? Ti sao?2) Lm th no chng minh protein c trong thc phm, trong len v t tm?Bi 6. THC HNH T CHN V HA HC HU CXcnhhmlngaxit axetylsalixylic(CH3COOC6H4COOH) ctrong thucaspirin(vin)bngphngphpthuphntrongkimvchun ngcvi dungdchchunlHCl haydungdchH2SO4vcht ch thphenolphtalein.I. Mc ch th nghimV nhiu l do, cc vt liu ng gi cho cc ng dng gia nh th thng c pha long bi cc hp cht tr, ng vai tr cht n. Trong trng hp ca cc dc phm, mt trong nhng l do cho vic lm ny l cung cp liu lng ng cho vin thuc c kch thc chp nhn c.V d aspirin (axit axetylsalicylic) th thng c trn vi mt cht n trong qu trnh tng hp thng mi. Mc ch ca thc nghim ny l xc nh phn trm aspirin thc c trong vin thuc.HS nghin cu phn ng thy phn este v thc hnh chun mt baz mnh bng axit mnh;96Tp phng php nghin cu khoa hc: Xc nh hm lng axit axetylsalixylic (CH3COOC6H4COOH) c trong vin thuc aspirin; II. C s l thuyt Aspirin (axit axetylsalixylic) l mt axit hu c c cha c este hu c. N c s dng rng ri trong y hc nh mt loi thuc gim au v nh mt loi thuc gim st. N thng c iu ch bng phn ng ca axit salixylic vi anhydrit axetic theo phn ng sau:axit Salixylic anhydrit axeticaxit axetyl salixylic axit axetic Mt lng axit axetylsalixylic c th c xc nh bi s chun vi mt baz mnh nh Natri hiroxitCH3COO-C6H4COOH(aq)+ OH-(aq) CH3COOC6H4COO-(aq)+ H2O(l)Khi x l vi mt dung dch natri hidroxit, aspirin b thy phn v hai axit sinh ra cng c trung ha ngay.CH3COOC6H4COOH + 2NaOH CH3COO Na + HOC6H4COONa + H2ONu dng mt lng d dung dch NaOH trong phn ng ny, th lng NaOH d c xc nh bng php chun vi dung dch axit. Tuy nhin, iu cn thit laxit dngchunphi khngtcdngvi natri axetat vnatri salicylat (chaicht nyuchanhnganionbaz). Cthtrnhiuny bng cch chn cht ch th l phenol (khong chuyn mu pH t 6,8 n 8,4) hoc phenolphatalein (khong chuyn mu pH t 8,3 n 10,0).Tuy nhin, axit axetylsalixylic cng l mt este nn d dng b thy phn khi chun vi mt baz mnh, do trong mi trng kim n b phn hy dn 97n sai st trong s phn tch. Nh vy, khi p dng phng php chun th tt c axit c mt trong dung dch s thy phn hon ton trong NaOH d. Mt mol axit trong aspirin phn ng va vi mt mol NaOH, mt mol este trong aspirin phn ng va vi mt mol NaOH. Nh vy s mol NaOH phn ng s gp i s mol aspirin, sau lng NaOH tha s c chun vi dung dch axit chun. Trong th nghim ny, axit acetylsalicylic s c chun b, tng lng acid c mt s c xc nh bng cch s dng mt phng php chun li.III. Dng c, Ha cht th nghimDNG C HA CHT cc, 100 ml, Bnh tam gic (Erlenmeyer) 250 mL Pipet, 5 ml v 10 ml Xi lanh c chia , 50 ml buret, 50 ml Thanh khuy HCl 0,3M;(R23/25/34/37-S26/36/37/45) NaOH 0,5M; (R35-S1/2/26/37/ 39/45) Etanol (lng)(R11/20/21/22/36/37/38/40), (S7/16/24/25/36/37/39/45) CH3COOC6H4COOH (tinh th) (R22/36/37/38/41-S22/26/36/37/39)Cht ch th phenolphtaleinIV.Cc bc tin hnh th nghim1. Cn cc vin aspirin c lng khong 0,5 g. Ghi li s vin v khi lng. Ha tan cc vin aspirin cn c vo 15 ml etanol trong mt bnh tam gic 250 ml.2. Thm 20 mL dung dch NaOH 0.50 mol.L-1.3. tng tc phn ng thy phn, un nng cc mu trong mt cc nc khong 15 pht. 984. Lm lnh mu n nhit phng v cn thn tt c vo mt bnh nh mc 250 mL. Ra bnh phn ng vi ln vi nc, thm phn ra vo bnh nh mc. Lm long dung dch n vch mc v lc k hn hp. Ly 25 mL hn hp phn ng pha long v n vo mt bnh nn sch, thm 2- 4 git ch th phenolphtalein vo bnh. Mu sc ca dung dch l mu hng nht.Nudung dchkhng muththm5mldung dchNaOH 0,50 mol. L-1 ri lp li cc bc 3 v 4.5. Ghi li tng khi lng dung dch NaOH 0,50 mol.L-1 c thm vo.6. Chun baz tha trong dung dch bng dung dch HCl 0,30 mol.L-1 cho n khi mu hng bin mt v dung dch tr nn c. Ghi li nng mol ca axit v cht chun thu c. Lp li s xc nh cho n khi no kt qu gn nh khng i. Tnh gi tr trung bnh.7. Ghi li khi lng dung dch HCl 0,30 mol.L-1 c thm vo.8. Lp li cc bc ca s chun hai ln na bng cch s dng hai mu mi.V. Mt s lu th nghim thc hin thnh cngTrnh un si, bi v cc mu c th b phn hy;Lm ngui hn hp phn ng bng cch gi bnh di vi nc ang chy;VI. Phn tch kt qu th nghim v Bo co1. Tnh lng axit axetylsalixylic c trong mu asppirinV d: S mol (axit axetylsalixylic) theo l thuyt= , g, g/mol100180 0 = 5.55 mmol40 ml NaOH 0,5 M cha 20 mmolChun 1,00 g mu vi HCl 0.30 M, thc nghim dng trung bnh 27.0 ml 27 ml HCl 0,3M cha 8,10 mmol n(NaOH dng phn ng vi axit axetylsalixylic) = 20.0 8.10 = 11.9 mmol1,0 mol axit axetylsalixylic phn ng vi 2,0 mol NaOH nnS mol (axit axetylsalixylic) = , 1192= 5.95 mmol99 loi b axit axetic to ra sau phn ng, qu trnh kt tinh li (ti kt tinh) c lp i lp li v ra sch mu bng nc d. Do lng mu gim t 1,50 g n 1,05 g.Trong s chun ti kt tinh1,00 g muvi HCl 0.30 M, thc nghim dng trung bnh 28.9 ml. (28,9 ml HCl 0,30M cha 8,67 mmol)n(NaOH dng phn ng vi axit axetylsalixylic) = 20,0 8,67 = 11,3 mmol1,0 mol axit axetylsalixylic phn ng vi 2,0 mol NaOH nnS mol (axit axetylsalixylic) = , 1132 = 5,67 mmol2. Tnh tinh khit ca aspirin v biu th bng t l phn trm khi lngim nng chy ca mu l 132oCch ra rng mu khng tinh khit.Khi lng axit axetylsalixylic tm thy trong (b) nhiu hn so vi l thuyt ch ra rng phng php tnh cho thy khng ch axit axetylsalixylic m cn axit salixylic v sn phm ph axit axetic cng khng phn ng. V vy n s nh hng n tinh khit ca mu aspirin.VII. Cu hi kim tra v m rng1) Ti sao cn phi lm ngui hn hp phn ng?2) Ti sao cn phi trn k hn hp phn ng?3)Pipet u tin nn c ra bng g?4)Nn ra bnh bng g?5) Ti sao cn pha long dung dch NaOH?6) Tnh khi lng ca axit axetylsalicylic trong mi vin thuc v so snh iu ny vi ghi ch trn hp v gii thch. 7) Phn tch k thut v kt qu ca bn trong th nghim ny. Lit k (theo mc quan trng), ngun gc li khc nhau c th xut hin trong phn tch ny.100Bi 7. PHN TCH NH LNG AXIT ASCORBIC TRONG VIN THUC VITAMIN CI. Mc ch th nghimMc ch ca TN ny l kim tra hm lng axit Ascorbic c trong vin thuc vitamin C thng mi (hm lng ghi trn bao b l 500 mg) Rn luyn cc k nng th nghim nh: cn, tn nh cht rn, ha tan cht rn, lc, s dng b thit b phn tch th tch, chun dung dch.II. C s l thuytThnh phn chnh trong vitamin C thng mi l axit ascorbic (H2C6H6O27, FW = 176,12). Axit ascorbicva l mtaxit, valmtchtkh, do,c chunaxit-baz vchunoxihakhu c th sdngxc nh lng axit ascorbic trong nhng vin vitamin C thng mi.Vitamin C l 1 cht chng oxy ha cn thit i vi dinh dng ca con ngi. Thiu vitamin C c th dn n bnh scurvy (scobat) c trng khin cho xng v rng khng bnh thng v mt s bnh khc. Vitamin C l tn thng gi ca axit L-ascorbic (AsA), c danh php quc t l 2-oxo-L-threo-hexono-1,4-lactone-2,3-enediol, CTPT C6H6O6(M= 176,1g/mol), CTCT nh sau:Trong cng thc cu to ca ascorbic ta nhn thy c C4 v C5 l 2 cacbon bt i xng, v vy ascorbic c 4 ng phn quang hc l axit L-ascorbic, axit izo L-ascorbic, axit D-ascorbic v axit izo D-ascorbic. Trong s cc ng phn ny ch c axit L-ascorbic v izo L-ascorbic l c tc dng cha bnh cn 2 ng phn cn li l cc khng vitamin, tc l c ch tc dng ca vitamin. Trong t 101nhin ch tn ti dng axit L-ascorbic, cc ng phn cn li c to ra theo con ng tng hp.Axit ascorbic tn ti dng tinh th hoc bt kt tinh trng hoc hi ng vng,khng mi,c v chua,tan nhiu trong nc (300g/lt),t tan hn trong ru v khng tan trong chloroform, benzene hay cc dung mi h c khng phn cc.Axit ascorbic rt d b phn hy di tc dng ca nh sng v nhit . Dungdchaxit ascorbickhngbn, rt db oxyhadi tcdngcaoxy khng kh, c bit l khi c mt mt s kim loi nng: Fe, Cu V vy cn phi bo qun vitamin C trong bng ti v nhit thp.Ha tnh ca vitamin C l ha tnh ca nhm chc lacton,ca cc nhm hydroxyl, calinkt i, songquantrngnht lnhmchcendiol. Chnh nhm ny quyt nh tnh axit v tnh kh ca axit ascorbic. Nguyn tc phng php1. Phng php axit bazTrong dung mi nc, axit ascorbic l axit phn ly hai nc vi cc gi tr pKa ln lt bng 4,2 v 11,6 tng ng vi s phn ly H+ ca nhm OH nh vo C3 v C2 .Axit ascorbic d dng phn ng vi cc dung dch kim to mui.+ NaOHHOH2C (CHOH)3COCOONa + H2OOHO OHOCH2OHHH OH nh lng axit ascorbic c th dng phn ng chun nc 1 vi NaOH, ch th phenolphatalein.1. Phng php oxi ha kh:Axit L-ascorbicb oxi hathnhaxit L-dehydroascorbictheobnphnng oxihasau y ( E0= 0,127V pH=5)102+ 2H++ 2e-OHO OHOCH2OHHH OHOOOOCH2OHHH OHAxit ascorbic Axit dehidroascorbicQu trnh oxy ha ascorbic xy ra hai mc khc nhau:- S oxy ha thun nghch vitamin C thnh axit dehydroascorbic: tnh cht ny v cng quan trng i vi tc dng sinh hc ca axit ascorbic l tham gia xc tc cc qu trnh oxy ha kh xy ra trong c th.- S oxy ha bt thun nghch bin vitamin C thnh cc sn phm khc khng c hot tnh v bin mu. Phn ng ny tng nhanh theo pH v nhit ca dung dch.Cc cht oxy ha thng dng oxi ha axit ascorbic l: dung dch AgNO3, thuc th Fehling, dung dch KMnO4, 2,6-diclorophenolindophenol, brom, iot... Phngphpchunctinhnhbngcchnhttdungdch thuc th t buret vo dung dch c cha axit ascorbic trong mi trng thch hp. im tng ng c nhn nh s chuyn mu ca dung dch khi c cht ch th thch hp. Phng php ny c th p dng xc nh trc tip vitamin C trong cc mu thc phm.Trong cc i tng khc nh rau qu, thc phm,nc gii khtc thnh phn tng i phc tp,cha nhiu cht kh khc nhau, dung dch c v c mu, gy kh khn trong vic xc nh im cui ca qu trnh chun .Trong th nghim ny hm lng vitamin C trong vin nn c xc nh bng phng php chun axit- baz hoc chun oxi ha kh. Axit ascorbic c xc nh da trn phn ng oxi ha n bng iot (trong KI d) theo phng php chun trc tip vi cht ch th h tinh bt. 103Th nghim ny gm hai phn, phn u dng chun axit-baz xc nh lng axit ascorbic trong mt vin vitamin C. Phn th hai dng chun oxi ha kh thc hin xc nh tng t.III. Dng c, ha cht th nghimDNG C HA CHT ng ong 10 ml; 100 ml Cc thy tinh 100 ml; 250 ml Bnh Erlenmeyer (bnh tam gic): 125 ml; 250 ml Giy lc Giy cn Khun v Phn mu Buret thng Buret Brush Bnh nh mc, 100 ml Tha Phu Pipet (20 mL) / Bm an ton Pipet Pasteur (ng nh git) Bn chi Dung dch NaOH(R35-S1/2/26/37/ 39/45)(0,1 M) Dung dch Iod (0.01 M) Dung dch Phenonphtalein Dung dch metyl Dung dch h tinh bt....IV. Cc bc tin hnh th nghimCn chnh xc vin vitamin C (c v), ha tan vin vitamin C trong nc, lc nu cn thit. Th tch cui cng ca dung dch nn l 100 mL. Cn li phn b ri tr i v ghi li khi lng axit ascorbic em TN.Chun b cc dung dch:* Dung dch vitamin C chun:Cn chnh xc lng c 0,1 gam axit ascorbic trn cn phn tch v chuyn nh lng vo bnh nh mc dung tch 250 ml. Thm khong 2 gam axit oxalic 104vo bnh nh mc, thm nh mc n 2/3 th tch bnh v lc u cho cht rn tan ht sau nh mc n vch mc bng nc ct. Nt kn bnh trnh s oxi ha ca oxi khng kh. Dung dch ny c dng chun dung dch iot.* Dung dch it:Ha tan 5 g KI v 0,268 g KIO3 trong 200 ml nc ct, thm 30 ml axit sunfuric 3 M v chuyn vo bnh nh mc 500 ml, nh mc n vch mc, ta c dung dch KI3Phn 1: Chun axit-baz.1-1 Dng pipet 10 mL ht dung dch trn cho vo mt bnh tamgic (Erlenmeyer). Chn cht ch th thch hp thc hin s chun .1-2 Lp li 3 ln bc th 2. Phn 2: Chun oxi ha kh2-1 Xc nh nng dung dch iot cho S dng dung dch thiosunfat chun xc nh nng dung dch iot cho.2-1-1 Dng pipet 20 mL a dung dch iodin vo bnh Erlenmeyer, ri chun bng cch s dng dung dch Na2S2O3 chun. Dng tinh bt lm cht ch th. 2-1-2 Lp li 3 ln bc th 4.2-2 Xc nh lng axit ascorbic.2-2-1 Dng Pipet 10 mL a dung dch t bc 1 vo bnh Erlenmeyer. Thm vo vi git tinh bt lm cht ch th v chun vi dung dch iod.2-2-2 Lp li 3 ln bc th 6.V. Mt s lu th nghim thc hin thnh cng Khi cn khng cn in t di qut trn hoc qut bnKim tra buret trn tru, nu khng trn th cn nh mt git glixerol vo kha buret S dng pipet my tht thnh tho trc khi TN105Dung dch iot d b kt tinh tr li lm cho nng thay i nn cn xc nh chnh xc nng dung dch iot trc khi TNVI. Phn tch kt qu th nghim v Bo coS nh gi c da trn s chnh xc ca mi php chun . Tnh 30% cho chun axit-baz, tnh 60% cho chun oxi ha kh v 10% cho s so snh hai phng php.1 Chun axit - bazChun ln 1 Dung dch Vitamin CmL; Dung dch NaOH dng mLChun ln 2 Dung dch Vitamin CmL; Dung dch NaOH dng mLChun ln 3 Dung dch Vitamin CmL; Dung dch NaOH dng mL2 Chun oxi ha kh2-1 Xc nh nng iotChun ln 1 Dung dch IodmL; Dung dch Na2S2O3 dng mLC