Chuyen de Nhan Biet Va Tach Chat Cuc Hay

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  • 1

    Chuyn 1: Nhn bit Tch cht

    1. S

    2. Nhn bit 2.1. V c 2.1.1. n cht 2.1.1.1. Nhn bit kim loi a. Nhng phn ng c trng ca kim loi

    Cht cn nhn bit Thuc th Hin tng Phng trnh phn ng

    Kim loi kim v kim th H2O

    Dung dch trong + H2 (i vi Ca cho dung dch

    c) M + nH2O M(OH)n + 2

    n H2

    Li (Li+) Tm ln a Ngn la ta

    Mui

    NHN BIT TCH CHT

    V C HU C

    N CHT

    HIROCACBON DN XUT

    Ancol

    Axit Este

    Amino axit

    HP CHT

    Ankin

    Ankan

    Ankaien

    Anken

    NO KHNG NO

    THM

    Xicloankan

    Kim loi

    Phi kim

    Baz

    Axit

    Oxit Anehit Xeton

    Amin

    Cacbohirat

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  • 2

    K (K+) Tm Na (Na+) Vng Ca (Ca+) da cam Ba (Ba+)

    Pt, ri t trn n kh khng

    mu Vng lc

    Nguyn t lng tnh:

    Be, Zn, Al, Cr

    Dung dch OH- (NaOH,

    Ca(OH)2) Tan + H2

    M + (4-n)OH- + (n-2)H2O MO2n-4 +

    2n H2

    M + (4-n)NaOH + (n-2)H2O Na

    n-4MO2 + 2n H2

    Pb HCl Kt ta trng + H2 Pb + 2HCl PbCl2 + H2

    HNO3 long Kh NO khng

    mu 3Cu + 8HNO3

    3Cu(NO3)2 + 2NO + 4H2O HNO3 c Kh NO2 mu nu

    Cu + 4HNO3 Cu(NO3)2 + 2NO2 +2H2O Cu

    t trong O2 Mu (Cu) Mu en

    (CuO) 2Cu + O2 2CuO

    Au

    Hn hp HNO3 c v HCl c t l th tch 1:3

    Tan + NO Au + HNO3 + 3HCl AuCl3 + NO + 2H2O

    Ba Dung dch H2SO4 long Kt ta trng v

    H2 Ba + H2SO4long BaSO4 + H2

    b. Mt s bi tp tiu biu: Bi 1: Bng phng php ha hc, hy phn bit bn kim loi sau: Al, Zn, Cu, Fe. Bi 2: Dng phn ng ha hc nhn bit tng kim loi sau: Al, Ca, Mg v Na. Bi 3: C 5 mu kim loi: Ba, Mg, Fe, Ag, Al. Nu ch c H2SO4 long (khng c dng

    bt k cht no khc k c qu tm, nc nguyn cht) c th nhn c nhng kim loi no? Bi 4: Ch dng mt ha cht, nu phng php nhn bit 4 mu kim loi sau: Mg, Zn, Fe,

    Ba. Bi gii

    Bi 1: Al, Zn, Cu, Fe Ly mt t ha cht lm thuc th: - Cho H2SO4 c ngui vo 4 kim loi:

    - Ch c Cu, Zn phn ng: Cu + 2H2SO4 c CuSO4 + SO2 + 2H2O Zn + 2H2SO4 c ZnSO4 + SO2 + 2H2O

    - Sau , Zn v Cu c phn bit bng HCl long, nh dung dch HCl long vo hai mu, mu no c si bt kh l Zn, mu khng tc dng l Cu.

    Zn + 2HCl ZnCl2 + H2 - Hai mu Al v Fe cn li, cho tc dng vi dung dch NaOH, mu no tan trong dung

    dich NaOH l Al, mu khng phn ng l Fe. 2Al + 2NaOH + 2H2O 2NaAlO2 (dd) + 3H2

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  • 3

    Bi 2: Al, Ca, Mg v Na Ly mt t ha cht lm thuc th: Cho nc vo 4 mu thuc th, hai mu phn ng l Ca, Na. Hai mu khng tc dng vi

    nc nhit thng l Al v Mg. Ca + 2H2O Ca(OH)2 + H2 2Na + 2H2O 2NaOH + H2

    Tip theo, thi kh CO2 vo 2 l dung dch va to thnh, l no to dung dch c l l ng Ca(OH)2, suy ra mu ban u l kim loi Ca. L no to dung dch trong sut l NaOH, suy ra mu ban u l Na.

    CO2 + Ca(OH)2 CaCO3 + H2O CO2 + 2NaOH Na2CO3 + H2O

    Cho dung dch NaOH vo hai mu cn li, mu no tan trong NaOH l Al, mu cn li l Mg.

    2Al + 2NaOH + 2H2O 2NaAlO2 (dd) + 3H2

    Bi 3: Ba, Mg, Fe, Ag, Al (ch dng H2SO4) Ly mt t ha cht lm thuc th: Cho 5 mu thuc th vo 5 ng nghim cha dung dch H2SO4 long. ng nghim no

    khng c bt kh thot ra l Ag. ng no c kh thot ra v c kt ta trng l Ba. Cc ng nghim cn li to dung dch trong sut v c bt kh thot ra (kh H2) gm Mg, Fe v Al.

    Cc phng trnh phn ng xy ra: Khi cho Ba vo axit H2SO4 th u tin xy ra phn ng:

    Ba + H2O Ba(OH)2 + H2 Tip theo:

    Ba + H2SO4 BaSO4 (trng) + H2 Mg + H2SO4 MgSO4 + H2 Fe + H2SO4 FeSO4 + H2 2Al + 3H2SO4 Al2(SO4)3 + 3H2

    Tip tc, trong ng nghim nhn bit c Ba, lc b kt ta BaSO4, cn li l dung dch Ba(OH)2. Cho 3 kim loi cn li gm Mg, Fe v Al vo 3 ng nghim cha dung dch Ba(OH)2, ng nghim no c kim loi tan ng thi c kh thot ra, l l ng Al.

    2Al + Ba(OH)2 + 2H2O Ba(AlO2)2 + 3H2 ng thi cho dung dch Ba(OH)2 vo hai l dung dch MgSO4, FeSO4. ng nghim no

    c kt ta trng ri bin thnh mu nu l FeSO4(do kt ta trng ca BaSO4 ha ln vi kt ta Fe(OH)2 mu xanh l a) ng vi kim loi Fe. ng nghim cn li l MgSO4 ng vi kim loi Mg.

    Phng trnh phn ng: Ba(OH)2 + FeSO4 BaSO4 (trng) + Fe(OH)2 Ba(OH)2 + MgSO4 BaSO4 (trng) + Mg(OH)2

    Bi 4: Mg, Zn, Fe, Ba - Ly 4 ng nghim, mi ng cha mt t dung dch H2SO4, cho ln lt tng kim loi

    vo cc kim loi trn, ng no c bt kh bay ra v xut hin kt ta l Ba. Cc phng trnh phn ng xy ra: Khi cho Ba vo axit H2SO4 th u tin xy ra phn ng:

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  • 4

    Ba + H2O Ba(OH)2 + H2 Tip theo:

    Ba + H2SO4 BaSO4 (trng) + H2 Mg + H2SO4 MgSO4 + H2 Fe + H2SO4 FeSO4 + H2 Zn + 3H2SO4 ZnSO4 + H2

    Tip tc, trong ng nghim nhn bit c Ba, lc b kt ta BaSO4, cn li l dung dch Ba(OH)2. Cho 3 kim loi cn li gm Mg, Fe v Zn vo 3 ng nghim cha dung dch Ba(OH)2, ng nghim no phn ng v c kh thot ra l ng nghim c cha kim loi Zn.

    Zn + Ba(OH)2 BaZnO2 + H2 Cho tip Ba(OH)2 vo 2 ng nghim cha cc dung dch MgSO4, FeSO4 c trn.

    ng nghim c kt ta trng v khng i mu l ng MgSO4, t suy ra kim loi tng ng l Mg. ng nghim cn li c kt ta mu trng sau chuyn sang mu nu l FeSO4, t suy ra kim loi cn li l Fe.

    FeSO4 + Ba(OH)2 Fe(OH)2 + BaSO4 MgSO4 + Ba(OH)2 Mg(OH)2 + BaSO4

    2.1.1.2. Nhn bit phi kim: (kh dng n cht) a. Nhng phn ng c trng:

    Cht cn nhn bit Thuc th Hin tng Phng trnh phn ng

    F2 Kh mu lc nht

    Nc Br2 Nc Br2 nht mu

    5Cl2 + Br2 + 6H2O10HCl + 2HBrO3 Cl2

    Dung dch KI + h tinh bt

    T khng mu mu xanh

    Cl2 + 2KI 2KCl + I2 H tinh bt + 2I Mu xanh

    Cht lng mu nu

    Nc clo Nc Br2 nht mu

    5Cl2 + Br2 + 6H2O10HCl + 2HBrO3

    Br2

    Kh SO2 Nc Br2 nht mu

    SO2 + Br2 + 2H2O H2SO4 + 2HBr

    un nng Tinh th thng hoa (hi mu tm)

    I2

    H tinh bt T khng mu mu xanh

    Que m tn

    Bng chy O2

    Cu (mu ),to CuO (mu en) 2Cu + O2 ot 2CuO H2 CuO (mu

    en), to Cu (mu ) H2 + CuO ot Cu + H2O

    b. Mt s bi tp tiu biu: Bi 1: Nhn bit cht kh: c cc l ng kh ring bit sau

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  • 5

    a- O2, Cl2, O3 b- N2, H2, Cl2, F2.

    Bi 2: Nhn bit cc kh sau cha trong cc l ring bit bng phng php ha hc: O2, O3, N2, Cl2. Bi gii

    Bi 1: a. Quan st mu ca cc kh ta thy mt trong nhng l kh c mu vng lc, l kh Cl2. Dng giy tm h tinh bt v dung dch KI nhn bit kh O3. O3 + 2KI + H2O O2 + I2 + 2KOH. L cn li ng O2. b. Quan st mu cc l kh ta thy, c mt l kh mu vng lc l Cl2. Mt l kh mu lc nht l l kh F2. Hai l kh cn li dng dung dch Ca(OH)2 nhn bit, l kh no lm dung dch Ca(OH)2 c th l l kh CO2. L cn li l H2.

    Bi 2: Quan st mu cc l kh ta thy l no c mu vng lc l kh Cl2. Dng giy tm h tinh bt v dung dch KI nhn bit kh O3. O3 + 2KI + H2O O2 + I2 + 2KOH. Hai l kh cn li a que dim cn m vo, l no lm que dim chy mnh l l ng kh O2. L cn li l N2.

    2.1.2. Hp cht 2.1.2.1. Nguyn tc

    - nhn bit mt ion trong dung dch, ngi ta thm vo dugn dch mt thuc th to vi ion mt sn phm c trng nh: mt cht kt ta, mt hp cht c mu hoc cht kh kh tan si bt, hay bay khi dung dch.

    - nhn bit mt kh, ngi ta c th da vo tnh cht vt l hoc tnh cht ha hc c trng ca n.

    Mt s hin tng nhn bit mt s ion (cation v anion): Cht th

    (thuc th) Thuc th (cht th) Hin tng Phn ng

    24SO

    Kt ta trng 2Ba + + 24SO BaSO4 2Ba + 23CO

    Kt ta trng 2 23 3Ba SO BaSO+ + 24SO

    Kt ta trng Ca2+ + SO42- CaSO4 2Ca + 23CO

    Kt ta trng 2 23 3Ba CO BaCO+ + OH Kt ta xanh 2 2( )Cu OH Cu OH+ + 2Cu + 2

    3SO

    Kt ta trng 2 23 3Cu SO CuSO+ + OH Kt ta trng 2 2( )Mg OH Mg OH+ + 2Mg + 2

    3CO

    Kt ta trng 2 23 3Mg CO MgCO+ + OH Kt ta trng xanh 2 2( )Fe OH Fe OH+ + 2Fe + 2

    3CO

    Kt ta trng 2 23 3Fe CO FeCO+ + OH Kt ta nu 3 3( )Fe OH Fe OH+ + 3Fe + 3

    4PO

    Kt ta trng 3 34 4Fe PO FePO+ +

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  • 6

    OH Kt ta en Ag OH AgOH+ + Ag +

    Cl Kt ta trng Ag Cl AgCl+ + Mn2+ OH Kt ta trng 2 2( )Mn OH Mn OH+ +

    3

    2

    2

    3

    AlZnBeCr

    +

    +

    +

    +

    To phc tan trong kim d

    4

    4

    4

    4

    [ ( ) ][ ( ) ][ ( ) ][ ( ) ]

    Na Al OHNa Zn OHNa Be OHNa Cr OH

    2.1.2.2. Nhn bit a. Oxit baz:

    Dng: Hn ch thuc th Bi 1. Ch dng HCl v H2O. Hy nhn bit cc cht sau y ng ring bit trong cc l

    mt nhn: BaO, MgO, MnO2, Al2O3, FeO, Fe2O3. Hng dn

    - Xem nhng oxit trn thuc loi oxit no (tan hay khng tan). - Cc oxit c to phc c hay khng. - Sn phm sau khi nhn bit c cht c th nhn bit c cc cht khc khng. - Cc cht s cho nhng du hiu g khi tc dng vi cht .(kt ta, kh thot ra, to

    phc). Tr li

    - Ly mi cht mt t lm mu th. - Cho nc vo tt c cc mu th, mu no tan th l BaO.

    BaO + H2O Ba(OH)2 - Cho HCl vo cc mu th cn li, mu no c kh xut hin th l MnO2.

    MnO2 + 4HCl MnCl3 + 12

    Cl2 + 2H2O Fe2O3 + 6HCl 2FeCl3 + 3H2O FeO + 2HCl FeCl2 + H2O Al2O3 + 6HCl 2AlCl3 + 3H2O

    - Dung dung dch Ba(OH)2 va nhn bit c trn cho vo ln lt cc mu th cn li:

    + Mu no c kt ta mu nu l FeCl3 Fe2O3 2FeCl3 + 3Ba(OH)2 2Fe(OH)3 + 3BaCl2

    + Mu no kt ta mu trng xanh l FeCl2 FeO FeCl2 + Ba(OH)2 Fe(OH)2 + BaCl2

    + Mu no c kt ta trng nhng tan trong Ba(OH)2 d l AlCl3 Al2O3 2AlCl3 + 3Ba(OH)2 2Al(OH)3 + 3BaCl2 Al(OH)3 + Ba(OH)2 Ba[Al(OH)4]2

    Bi 2. Ch dng mt ha cht hy nhn bit cc l dng oxit mt nhn sau: Na2O, Al2O3, Fe2O3, MgO

    Dng: Khng hn ch thuc th Bi 1. C 4 l ng 4 oxit dng bt b mt nhn sau: CuO, Al2O3, MgO, Fe2O3

    Hng dn - Nhng oxit u dng