phan tich thuc pham . hay.ppt

7/31/2019 phan tich thuc pham . hay.ppt

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Chuyen e 2NHNG NGUYENTAC KY THUAT C BAN S

DUNG CHO PHAN TCH THCPHAM


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I/ NHNG PHNG PHAPPHAN TCH CO IEN

1/ PHN TCH TH TCH 1.1 Phng phapchuan o Axt Baz

1.2/Phng phapchuan o phc cht 1.3/ Phng phapchuan o oxi hakh 1.4/ Phng phapchuan o kt ta

2/ PHAN TCH BANG PHNG PHAP TRONGLNG


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II/ PHNG PHAP PHAN TCHHIEN AI

1/ Phng phap phan tch quang pho

Quang pho hap thu nguyen t(AAS) Quang pho phat xa Plasma (ICP)2/ Phng phap phan tch sac ky

Phng phap phan tch bang sac kykh (GC) Phng phap phan tch bang sac kylong (HPLC)


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I/ PHAN TCH THE TCH (chuan o Titrimetric analysis)

1/ Nong o cua dung dch dung trong phan

tch

2/ Chuan o axt baz ( Acide- basetitrations)

3/ Chuan o oxyhoa kh ( redox titrations)

4/ Chuan o ket tua ( Precipitation


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Moi lien he gia 3 loai nongoCM = C% . 10. d , CN = C% .10. d

M

CN = M. CM , CM = so mol . chat tan(n)

so kg dung moiM : khoi lng mol phan t chat tan : ng lng g chat tand : Ty trong rieng cua chat tan

CM = a gam chat tan. 1000ml dung dch M .V

M: khoi lng phan t chat tan


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PHA DUNG DCH T CHAT RAN1/ Tnh toan lng can2/ Hoa tan3/ nh mc4/ Chuyen vao chai cha5/ Hieu chnh nong oMcan = CM . V. M

10. P%V : the tch tnhP% : o tinh khiet cua hoa chatM : phan t gamC

M: nong o mol

V du : Tnh lng can NaOH co P = 96% e phac 200ml dung dch NaOH 0,1Mmcan = 0,1. 200. 40 = 0,83g NaOH

10 . 96


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Pha dung dch t chat long1/ Tnh toan the tch can dung2/ Pha loang3/ nh mc4/ Chuyen vao chai cha5/ Hieu chuan lai nong o neu can

CM = C% . 10. d , Vcan lay = Ccan pha . Vcanpha M CM

V du : Tnh the tch H2SO4 98%, d= 1,84 can lay epha 200ml dung dch H2SO4 co nong o 1MCM = 10. 98. 1,84 = 18,4 M 98V can lay = 1. 200 = 10,87 ml 18,4


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Acide- base Titrations


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1/ Chuan o axt baz( Acide- base titrations)

Noi dung bai hoc - nh ngha ve Axt Baz

- Quan he gia Ka va Kb cua cap axt bazlien hp- Can bang dung dch

- pH cua dung dch,thiet b o pH va ch th

mau pH - Xay dng phng phap chuan o axtbaz

- Bai toan ng dung


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nh ngha phan tch chuano

Phan tch chuan ola o the tchcua dung dch a biet c nong ochnh xac cua chat chuan va chat

chuan o phan ng hoan toan vidung dch a c chuan b t mauthc pham can phan tch. - e xac nh iem tng ng chnhxac( point equivalent ) khi ket thuc chuan

o phai s dung ch th hoa hoc khi

mau cua ch thi thay oi


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V du : Xac nh o axt trong nc mam Dung dch chuan : NaOH 0,1N Ch th e xac nh iem tngng :

phenolphtalein : chuyen t khong mau tm oMau phan tch : 20ml

The tch chuan o c : 5 ml o axt = V x 0,1N x1000 =25mldlg/l

20


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CHUAN O AXT - BAZ

1/ KHAI NIEM AXT BAZ 1.1. Cac luan iem can banTheo ly thuyet ien ly cua Arrhenius :

- axt la nhng chat trong nc ienly cho cation H+ va anion goc axt- Baz la nhng chat ien ly cho anionhydroxyt OH va cation goc baz v du: HCl H+ + Cl- NaOH OH - + Na+


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Chuan o axt baz la phan ng trunghoa cua axt va baz cho muoi va ncthc chat la phan ng ket hp cua proton

vi anion hidroxytHCl + NaOH = NaCl + H2O thc chat

H+ + OH- H2O

Nam 1923 ly thuyet Proton cua hai nha khoahoc Bronsted va Lowry a m rong khainiem axt baz nh sau:

Axt la tat ca phan t hoac ion co kha

nang cho proton H+

Baz : la tat ca phan t hoac ion cokha nang nhan proton H+Chat va co kha nang cho Proton, vua co

kha nang nhan Proton goi la chat lng


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V du

Axt : cho proton H+ Baz lien hp

CH3COOH - H+ CH3COO-

NH4+ _ H+ NH3

HC2O-

_ H+

C2O42-

Baz : nhan proton Axt lien hpOH- + H+ H2O

HCO3- + H+ H2CO3H2O + H+ H3O+


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Proton khong ton tait do. Mot chat chthe hien tnh axt khi co mat mot baz e

nhan proton. Ngc lai mot chat ch thehien tnh baz khi co mat mot axt e choproton. Thc chat cua mot phan ng giamot axt vi mot baz la s chuyen proton (tc cho nhan proton)V du :

CH3COOH + NH3 CH3COO- + NH4+

CH3COOH/ CH3COO- : mot cap axtbaz lienhp,

NH3// NH4+ mot cap axtbaz lien hp th 2

V d 2


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V du 2 :

CH3COO- + H2O CH3COOH + OH-

H+ chuyen t H2O sang cho CH3COO-

Tom lai theo ly thuyetprotonphan

ng axt baz co s o sau:

Axt (1) + Baz( 2) Baz (1) + Axt (2)

Chuyen H+t axt BazAxt(1)/ baz (1) va Axt(2) / baz (2) lahai cap axt baz lien hp


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1.2. Khai niem o manh cua axt vacua baz

Theo Bronsted Lowry o manh cuaaxt the hien kha nang cho proton , o

manh cua baz the hien kha nangnhan proton , Phan ng : xay ra hoan toan khi

HCl + H2O H3O+ + Cl-Axt HCl manh hn H3O+Baz H2O manh hn Cl-

Tom lai axt cang manh bao nhieu th


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1.3/ Bang o manh tng oicua cac cap axtbaz lien hp

Tnh axt giam dan

Axt lien hp : HClO4 H2SO4 HCl HNO3 H3O+

H2SO3Baz lien hp: ClO-4 HSO-4 Cl- H2O H2OHSO3-

Tnh baz tang dan

e xac nh cu the o manh cua axt hay bazngi ta da vao hang so K

Ahoac hang so

K

B


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1.4/ QUAN HE HANG SO KA VA KBe xac nh cu the o manh cua axt haybaz ngi ta da vao hang so K

Ahoac

hang so KBChon H2O lam dung moi e so sanhTrng hp 1: dung dch n Axt Axt : A + H2O B + H3O+

Ap dungnh luat tac dung khoi lng

K = aBxaH3O+ K = [B][H3O+] aA x aH2O [ A] [H2O]

Rut ra : Kx[H2O] = [B][H3O+] = KA hay pKA = - lgKA[ A]


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V d : CH3COOH co KA = 1,86.10-5

HCN co KA = 7,20.10-10

t pKA = - lgKA ( pKAch s axt) suy ra

pKA ca CH3COOH = 4,73 pKAca HCN = 9,14Kt lun: Hng s KA cang ln co ( tc ch so axtpKA cang nho ) th lc axt cang manh

Chu y . Vi cac axt a chc yeu s ien ly xay raqua nhieu giai oanV du : H3PO4 phai qua 3 giai oanH3PO4+ H2O H2PO4 + H3O+ K1 = 7,5.10-2 pK1 = 1,12

H2PO4+ H2O HPO4 + H3O+

K1 = 6,23.10-8

pK2 = 7,21HPO4+ H2O PO4 + H3O+ K1 = 2,2.10-13 pK1 = 12,66


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Trng hp 2 : dung dch n BAZ : B

B + H2O = A + OH-Ap dungnh luat tac dung khoi lng

aAxaOH-

K = aB x aH2O neu dung dch loang K =[ A] [OH-] [ B] [H2O]

Rut ra : KBx[H2O] = [A][OH-] = KB

[B] KB : Hang so baz:

Ch so baz : pKB = - lg KB


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Ket luan : Hang so baz cang ln(tc ch so baz pKB cang nho ) thbaz o cang manh

V du : so sanh hai chat bazNH3 : KNH3 = 1,79x10-5, pKNH3 = 4,75Anilin : KC6H5NH2 = 4.10

-10, pKC6H5NH2 = 9,4

suy ra NH3 > C6H5NH2


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1.5/ TCH SO ION CUA NC

Nc la chat ien ly rat yeu valng tnh H2O H+ + OH-

K = [H+].[OH-] , [H2O]

K. [H2O] = [H+

].[OH-

], KH2O=10-14

,pKH2O =14nc trung tnh va nguyen chat nen[H+] =[ OH-]= 10-7


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Da vaonong o cua ion H+ va ionOH- e biet c tnh chat moi trngcua mot dung dch . e bieu th moitrng ngi ta s dung ai lng pHhoac ch so pOH vi quy c: Ch so hidro pH = - lg[H+]

Ch so Hydroxyt pOH = - lg [OH-] pH + pOH = 14 suy ra pH = 14 - pOHDung dch trung tnh : pH = 7

Dung dch axt pH < 7Dung dch baz pH > 7


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Lien he gia KA va KB cua motcap

axt baz lien hpKA = [B].[ H3O+] KB = [A] .[ OH-] [A] [B]

Nhan vi ve cua hai phng trnh

KAx KB = [ H3O+] . [OH-] = KH2O

Vay pKA+ pKB = pKH2O = 14

T o cho thay axt cang manh thbaz lien hp cang yeu va ngc lai

baz cang manh th axt lien hp cang


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Bai tap :

1/ Tnh pH cua dung dch axt HCl, co nong o0,001M HCl la axt manh ien ly hoan toan[H3O+] = 10-3 suy ra : pH =3

2/ Hoa tan 0,6g NaOH vao nc thanh 1l dungdch .Tnh pH cua dung dchGiai : Tnh nong o cua NaOH = 0,6g : 40g =

0,015MNaOH manh ien ly hoan toan [ OH-] = 0,015M [ H+ ].[OH-] = 10-14T ay [H+] = 10- 14 : 0,015 = 6,6.10-13

pH = 12,18


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TNH pH CUA CAC DUNG DCH

pH dung dch axt manhGa s co mot dung dch axt manh HA nong

o au la CA HA H+ + A- H2O H+ + OH-nh luat bao toan nong o au : [A-] = CAnh luat trung hoa ien: [H+] = [A-] + [OH-]

Tch so ion cua nc : Kw = [H+]. [OH-]Suy ra : [H+] = [A-] + [OH-] = CA + Kw [H+]

[H+]2 - CA.[H+] Kw = 0


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[H+]2 - CA.[H+] Kw = 0

a/ CA > 10- 7bo quanong o[OH-] cuanc

[ H+ ] = CA suy ra pH = pCA


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pH dung dch baz manh

B + H2O HB+

+ OH-

H2O H+ + OH-

Theo L bao toan nong o au: HB+ = CBL trung hoa ien : [OH-] = [HB+]+ [H+]

Tch so ion cua nc : Kw = [OH-].[H+] Suy ra : [OH-] = [CB] + [H+] CB + [H+] = Kw

[H+

]

[H+]2 + CB.[H+]- Kw = 0


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Tng t nh trng hp axt manh:

a/ neu CB >> 10-7 co the bo qua H+

[OH- ] = CB hay pOH = - lgCB hay [ H+] = KwCB va pH = 14 pOH hay pH = 14 + lgCB

b/ Neu CB


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V du :Tm pH cua dung dch KOH 10-7

Giai phng trnh : [H+

]2

+ 10-7

[H+

] 10-14

= 0[H+] = 6,18 .10-8 , pH = - lg ( 6,18 .10-8) = 7,21

V du : Tnh pH dungdch KOH co nongo 10- 5

[ OH

-

] = CB = 10

-5

, pH = 14lg10-5

= 9


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pH cua dung dch n axt yeu

Ga s co dung dch n axt yeu HA, nng ul CA

HA H+ + A- KA = [H+ ].[ A- ] (1)

H2O H+ + OH- [HA]

Do axt yu khong phan ly hoan toan cho nentrong dung dch s tn ti hai nng :

CA : nng u HA + A-: nng phn ly v cha c phan ly ht

Cho nen : CA = [ A- ] + [HA] (2) [HA]= CA- [ A- ]

H+

= [A-

] + [ OH-

] (3) [A-

] = [H+

][OH-

]-


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T (3) co : [ A- ] = [H+ ] - [ OH-]T (2)Co : [HA] = CA - [A-] hay [HA] = CA - [H+ ] + [ OH-] th [HA] vao (1)

Ta co :[H+ ] = KA . [HA] = KA . ( CA - [H+ ] + [ OH-])

[A-

] [H+

] - [ OH-

]

[H+ ] = KA(CA - [H+ ] + [ OH-] ) [H+ ] - [ OH-]


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Xet cac trng hpa/ Nu [H+] >> [ OH-] tc la axt tng i mnh

( pKA 3) th

[H+ ] KA(CA - [H+ ] [H

+

]V d : tnh pH ca dung dch axt salixylic 10-3

( pKA

= 3)[H+] = 10-3 x 10-3[H+] [H+]T [H+]2 + 10-3 [H+]10-6 = 0

Gii phng trnh : [H+] = 6,2 x10-4 pH=3,21


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b/ Nu [OH-]


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Vd 2: Tm pH dung dch NH4 Cl 0,1M,biet pKB ( NH3) = 4,75Giai : pKA (NH4+ ) = 14pKB ( NH3) = 14 4,75= 9,25 pH = ( 9,25 lg 10-1 ) = 5,13


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pH dung dch n bazyuGa s co mt n baz yu B, nng u CB

B + H2O BH+ + OH- KB = [OH-].[BH+] (1) [B] H2O H+ + OH- ( Kw)

V baz yeu cho nen s phan ly cua n chat baz xara khong hoan toan v vay nong o ban au CB bao gc :

CB = [B] + [BH+

] (2) [BH+] + [H+] = [OH-] suy ra [BH+] = [OH-] - [H+] [B] = CB - [BH+] = CB - [OH-] + [H+]

[OH-

] = KB [B] = KB. CB [OH-

] +[ H+

] + - +


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Bit ga tr ca [OH] ta tnh c [H+]

va pH dung dch [H+] = Kw = pH = - lg [H+] [OH-]

Xet cac trng hp sau:

Xt cc trng hp:


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Xt cc trng hp:a/[H+]


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b/[H+]


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CONG THC TONG QUAT

KA = [B][H3O+

] KB = [A][OH-

] [A] [B]

Kw = [H+] [OH-] = 10-14

pH + pOH = 14 suy ra pH = 14pOH

pKA + pKB = Kw= 14

pH axt manh pH baz manh

[H+ ]2 - CA[H+] Kw = 0, [H+ ]2 - CB[H+] Kw =Oa/ CA


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b/ CA 10-7 b/ CB 10-7

[H+]2 -10-7[H+]-10-14 =0 [H+]2 +10-7[H+]-10-14 =0

C/ CA >> 10-7 C/ CB >> 10-7

[H+] = CA pH= pCA [OH-] = CB [H+] = Kw

CB


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pH dd n axt yu pH dd.n ca Bazyeu

[H+ ] = KA x(CA - [H+ ] + [ OH-] ) [OH- ] = KB x(CB - [OH- ] + [ H+ )[ H+ ] -

[ OH

-

][ OH- ] -

[ H

+

]

a/ [H+] >> [OH-]axt mnh a/ [H+]


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Chun axt manh bang bazmanh

Ga s lay 100ml HCl 0,1N em chuan o bangdung dch NaOH 0,1N. T cong thc pH = -lg[H+]se tnh c pH thay oi trong qua trnh trung hoa

axt manh bang baz manh.Trc khi chuan o dung dch HCl 0,1N :pH = -lg[H+] = -lgCHCl = -lg10-1 =1 Neu them 50mlNaOH 0,1N th dung dch con lai

50% HCl, khi them 99ml NaOH th dung dch con lai1% HCL .trong qua trnh them NaOH th nong o H+cua dung dch se b thay oi.e tnh nong o cua CHCl s dung cong thc :


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CA= ( VA - VB). NA

( VA + VB) hay

( VHCl - VNaOH).NHCl / ( VHCl + VNaOH)VA : the tch ban aung vi nong o NAVB : the tchthe tch dung dch chuan ngvi nong o N

BKhi them 50ml NaOH tc la HCl trung hoac 50%

CHCl = [H+]= ( 100 50) 0,1/ 150 = 3,3.10-2 M/l

pH = -lg [H+] = 2 lg3,3 = 1,5Tai iem tng ng tc la 100ml HCl =100mlNaOH suy ra pH = 7


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Trng hp chuan o qua

1001mlNaOH 0,1Nthsetnhlng kiemd

CNaOH = [OH-] = ( 0,1:200,1).0,1 = 5.10-5

pH = 14 pOH = 14 - 4,3 = 9,7

Luc au chuan o pH cua dung dch

thay oi cham gan en iem tngng thay oi rat nhanh sau iemtng ng lai thay oi cham


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Chuan o axt yeu bangbaz manhTnh pH khac nhau khi chuan o axt bang

kiemV du: CH3COOH 0,1N chuan o = NaOH 0,1N

Tnh pH iem 0 trc khi chuan o

KCH3COOH = 1,82.10-5pKCH3COOH = - lgKA = 5- lg 1,82 = 4,74

Thay ga tr pKCH3COOH,,va lgCCH3COOH vaocong thcpH = 4,74 + 1/2lg0,1= 2,37 + 0,5 = 2,87

Vay pH cua CH3COOH = 2,87

Trong qua trnh chuan o th pH cua dung

dch se thay oi nh sau:


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Trong qua trnh chuan o trong dung dch ton taico axt yeu CH3COOH , NaOH va muoi cua notao thanh mot dung dch em

Khi them50ml NaOH:pH = 4,74 lgCH3COOH.0,1N + lg( 50/100).0,1N = 4,74

Khi them 90mlNaOH : hon hp axt yeu va muoi

cua no pH = - lg[H+] = pKAlgCA + lgCKhAnpH = 4,74 lg( 10/100)0,1 + lg( 90/100).0,1 = 4,74 +2-1,05 = 5,69

iem tng ng khong trung vi iem trunghoa tc la khong trunng vi thi iem xay ras oi mau cua chat ch th b oi mau pH= 7 cho nen s ket thuc cua chuan o khongphai luon ket thuc pH=7


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CHUAN O BAZ YEU BANG AXTMANH

pOH = pKktOH - 1/2lgCKTOH

Khoang chuyen mau cua mot so

ch th thng gapMetyl da cam : 3,1 - 4,4 vang vangda cam

Metyl o : 4,4 - 6,2 o vangPhenolphtalein : 8,0 -10 khong mau -tm


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DUNG DCH MDung dch m l dung dch cto thnh khi trn

ln mt axt yu vi bazlin hp ca n hoc mt bazyu vi axt lin hp ca n. V d: dung dch m : CH3COOH v CH3COO-, hayhn hp gm NH3 /NH4+

Dung dch m c c im l pH thay i rt t khithm mt lng axt hoc bazHA + H2O H3O+ + A-

Khi thm mt lng axt (H3O+ ) :

H3O+ + A- HA axtyuNgc li khi thm OH- :

OH- + H+ = H2O ba zyu


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pH dung dch m:HA H+ + A- KA = [H+] [A-] / [HA]NaA- Na+ + A-

H2O H+ + OH- Kw = [H+] [OH-] / [H2O]Ta c KA = [H

+] [A-] [H+] = KA .[HA][HA] [A-]

Kw

= [H+][OH-]

[H+] + [Na+] = [OH-] + [A-] [H+]+ CB = [OH-] + [A-]Suy ra : [A-] = [H+] + CB[OH-]

[HA] + [A-

] = CA + CB [HA] = CA + CB[A-

][HA] = CA + CB - [H

+] + CB[OH-][H+] = KA [HA] = KA CA - [H

+] + [OH-]

[A-] CB + [H

+][OH- ]


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S ton tai cua HA va A- trong dungdch ngan can s tao thanh H+ va

OH- , khi tnh gan ung co the bo qua[H+] va [OH-]

[H+] = KACA suy ra pH = pKA lg CA CB CB


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V d: Tnh pH ca dung dch CH3COOH 0,01M vCH3COONa 0,01M

Gii: pH = pKA (CH3COOH) + lg 0,01 = 4,75

0,01

Gi thit thm 10ml dd NaOH 0,1M vo 1000ml dd m trn lc

:[H+] = KA 0,01 - 0.001

0,01 + 0,001

pH = pKAlg 0,81 = 4,84

pH dung dch thay i : 4,844,75 x100% = 1,89% 4,75


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PHA DUNG DCH CHUAN AXT VA BAZ


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NH NGHA CHT CHUN GC

1/ Cht gcC tnh n nh cao

Bn vi mi trngng lng ln

Khi lng ng vi cng thc ha chtPhn ng nh lng H2C2O4.2H2O ,

C6H5COOH

Na2B4O7.10H2OK2Cr2O7 ; NaClKMnO4, ZnSO4.7H2O ; MgSO4.7H2O


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2/ Chat goc dung e pha che cac dungdch chuan axt va baz

- Chuan o cac baz phai co dung dchchuan axt HCl, H2SO4.HCl thng hay c s dung hn ca v cac

muoi cua no thng tan. Khi pha mau canun soi th hay s dung H2SO4- Chuan o cac axt phai co dung dchchuan la baz

NaOH, KOH,Nong o cua dung dch chuan thay oi t0,01N en 0,2N . S dng dung dch 0,5N hay 1Nsau pha long thnh cc dung dung dch c nng

nh hn .

PHA CAC DUNG DCH


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PHA CAC DUNG DCHCHUAN

1/Neuaxt hay kiem ban au la chat longth ta o khoi lng rieng cua no, t o tratrong so tay hoa hoc se xac nh cnong o % cua chat co trong chat long

2/ Pha loang s bo dung dch am ac enthe tch gan bang the tch pha , sau o xacnh lai chnh xac bang mot dung dchchuan khac.

3/ Neu axt hay baz ban au la nhng chatran e pha dung dch chuan ta can motlng can thch hp cua chat ban au trong

mot the tch can thiet bang nc

XAC NH KHOI LNG RING CUA


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XAC NH KHOI LNG RING CUADUNG DCH

nh ngha : Khoi lng rieng (d) laty so khoi lng cua vat(g) va thetch (V) cua no

Khoi lng rieng c bieu dien : g/cm3 , g/ml d = g/V hay d = m/VXac nh khoi lng rieng :

ty trong ke, hoac phu ke

PHA DUNG DCH HCl 0 1N


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PHADUNG DCH HCl 0,1N

V du : pha 2 lt dung dch HCl co nong o 0,1N

- o khoi lng rieng cua HCl ac ban au bangty trong ke : p = 1,179g/cm3. Tra bang tng ng HCl36%- Trc het phai tnh neu HCl 100% e pha 2 ltdung dch HCl 0,1N

lg HCl = 36,46N .0,1. 2 = 7,292gHCl- Sau o tnh cho dung dch 36%

100g -------36ggHCl -----7,292

suy ra : g (HCl) = 7,292.100/ 36V (HCl) = m / d vay

7,292.100 / 36 / 1,179 = 17,2mlHCl acNh vay e pha 2 lt dung dch HCl 0,1N ta lay 17,2mlHCl (p=1,179g/cm3) bang ong ong cho vao bnh nh

mc 2lt va pha loang bng nc cat

2/ X h h d d h


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2/ Xac nh o chuan cua dung dchHCl 0,1N

- Co 2 phng phap xac nh ochuan cua HCl 0,1N - Phng phap the tch bang kiem

- Phng phap khoi lnga/ Phng phap the tch bang kiemNa2CO3 khan, Na2B4O7.10H2O, Na2C2O4..

NaOH 0,1N va ch th mau laphenolphtalein chuyen mau t trangxang tm hong

PHA CHE DUNG DCH KIEM NaOH


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PHA CHE DUNG DCH KIEM NaOH0,1N

NaOH tinh the mau trang, rat hut am

no b n ra trong khong kh va dedang phan ng vi CO2 cua khongkh. V vay thanh phan khong on nh

nen khong s dung NaOH lam chatchuan goc e pha che dung dchchuan o c.

Muon pha 2 lt dung dch NaOH 0,1N thcan mot lng NaOH 100% la:

NaOH = 40g, g (NaOH) = 40.0,1.2 = 8g

Ga s khoi lng rieng p cua

2 O 0 1


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e phathanh 2 lt dung dch NaOH 0,1Ncan lay lng can dung dch NaOH

26% la 100g ----------26g g NaOH--------8g suy ra g = 100.8/26

Vay the tch dung dch NaOH can lay: V= m/ d V = 100.8/26 / 1,285 = 24mlXac nh lai o chuan cua NaOH

0,1N - Axt oxalic H2C2O4.2H2O loai PA - Axt Benzoic C6H5COOH loai PA


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Xac dnh o chuan cua NaOH 0,1N theoAxtoxalic H2C2O4.2H2O

H2C2O4 H+ + HC2O4HC2O4 H+ + C2O4 lg H2C2O4.2H2O = M H2C2O4.2H2O / 2 =126,0662/2 = 63,033

iem tng ng pH = 8,55 , ch th mau laphenolphtalein t mau tm xang khong mau S co mat cua axt CO2 la axt co khanang tham gia phan ng tao thanh Hydro

cacbonat va cabonat gay can tr cho quatrnh chuan o bang axt oxalic do o khi phadung dch chuan axt oxalic nc cat phaic un soi e ui het CO2


64/200

Cong thc tnho chuan T

NNAOH = VH2C2O4.2H2O . NNa2H2C2O4.2H2O /VNaOH

TNaOH = NNaOH NaOH 1000


65/200

CHUN KT TA


66/200

CHUN KT TAPhng phap chuan o ket tua la datren phan ng hoa hoc cua chat canphan tch vi mot chat khac biet nong o( chat chuan) va ket thuc chuan o taoket tua hoan toan . Tai iem ket tuahoan toan tc la iem tng ng phai

s dung chat ch th tao s chuyen oimau .Phng phap ket tua gan lien vi s taothanh hp chat t tan cua Ag, Ba, Hg, Pb,Zn..vi mot so nguyen to khac

V d: chuan o Ba++ bang ion sunphat datren phan ng Ba++ + SO4 BaSO

4

Ngi ta dung Natri rodizonat e xac


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Ngi ta dung Natri rodizonat e xacnh iem tng ng khi d Ba++ dung

dch dung dch se chuyen mau t oxang trangV d 2: Xac nh ham lng Cl- trong

mu nc ung

AgNO3 + Cl- AgCl + NaNO3

Xac nh iem tng ng nh ionAg+ kt hp vi CrO4d tao thanhAg2CrO4 mu o gach cua

Phn php kt t h php nh ln


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Phng php kt ta cho php nh lng ccanion kt ta vi cc cation Ag, Ba, Hg, Pb,

Znv dcc clorua, bromua, iodua.cng nhcc cation to kt ta t tan vi cc anion k trn

Yeu cau oi vi phan ng c

dung trong phng phap ket tua :- Phan ng tao ket tua hoan toanva phan ng xay ra nhanh

- Ket tua c tao thanh co o tanthap nhat va co o tan cho phepkhong c vt qua 10-5 M/ l

Tch so tan va o tan


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Tch so tan va o tan1/ Tch so tan ien ly AgCl Ag+ + Cl- ket tuaTong quat chat ien ly t tan

ien ly AmBn mAn+ + nBm-

ket tuaAp dung nh luat tac dung khoi lng ta

co TAmBn = [An+]m[Bm-]n = constTAmBn : tch so tanTch so tan la mot hang so can bang ,

o ln cua no ch phu thuoc banchat chat tan va nhiet o

2/ o tan S


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2/ o tan :S m+n

SAmBn= [A+n ]m= [B-m]n = TAmBn

V du: Tnh tch so tan cua BaSO4 ,biet o tan cua no 200C la1,05.10-5M

Giai: T = [ Ba2+ ][SO42-]T = 1,0510-5 x 1,05.10-5 = 1,1.10-10

d 2 T h t h t A C O


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v du 2 : Tnh tch so tan cua Ag2CrO4biet rang 00C 100ml dung dch bao

hoa cua no cha 0,002156g Ag2CrO4

Giai :

Tnh so mol cua Ag2CrO4 so mol = 0,002156 x1000 = 6,5.10-5

331,73 x100 T = ( 6,5.10-5 )2 x 6,5.10-5 = 1,1.10-12

S tao thanh va s hoa tan mot


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S tao thanh va s hoa tan motket tua chat ien ly t tan

Theo quy tac tch so tan , chat ien ly t tan

se ket tua khi tch so tan nong o cac ion( vi so mau thch hp) vt qua ga tr tchso tan nhiet o a choNeu tch so [An+]m[Bm-]n trong dung dch

ln hn ga tr TAmBn th se tao thanh kettuaNeu [An+]m[Bm-]n < TAmBnket tua khongtach ra ma b hoa tan. S them bat ky ion nao tao thanh hpchatAn+ B-m eu lam giam o tan.Viec them cac chat ien ly khac khongco ion chung vi hp chat An+ B-m lam

tang o tan


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V d : Trn 1l dung dch Pb(CH3COO)20,05M vi1l dung dch KCl 0,5M. Hi kt ta PbCl2co xut

hin khong? Biet tch so tan cua muoi PbCl2 nhiet o thng la 1,6.10-5

Giai : Ta co CPb+2 = 2,5.10-2M , CCl = 2,5.10-1

CPb

2+ x CCl

2 = 2,5.10-2 x ( 2,5.10-1)2 = 1,56.10-3 >1,6.10-5

V tch so nong o cac ion vt qua ga trtch so tan nen mot phan PbCl2 se ket tua

Pb( CH3COO)2 + 2 KCl = PbCl2 + 2CH3COOK

V du 3:


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V du3:Tnh o tancua AgCl khi them vao dung dch bao hoacua no dung dch AgNO3 0,001N hay dung dch NaCl

0,001NGai :o tan SAgCl = [Ag+] = [Cl-] = TAgCl = 1,7.10-10 = 1,3.10-5M/l

a/ o tan cua AgCl khi them AgNO3 0.001N ngha latrong dung dch d Ag+ bangSAgCl = [Cl-] = TAgCl 1,7.10-10 : 1.10-3 = 1,7.10-7 M/l

[Ag]

b/ o tan cua AgCl khi them NaCl ngha la d ClSAgCl = [Ag+] = TAgCl 1,7.10-10 : 1.10-3 = 1,7.10-7 M/l

[Cl]Nh vay o tan cua AgCl se giam i mot cach ong

nhat khi them d ca ion Cl-

va ion Ag+


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CAC PHNG PHAP PHANTCH THC PHAM CO IEN CHUAN O AXT BAZ KET TUA


76/200

Lo hang ong nhat : La lo bao


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Lo hang ong nhat : La lo baogom nhng san pham cung ten

goi , cung mot loai pham chat,ng trong cung mot loai bao b,cung mot kch thc,

- Phai xem tnh trang cua bao bva c nghi nhan bang vanban

-Mau hang lay em i kiemnghiem phai la mau trung bnh,ngha la sau khi chia thanh lohang ong nhat , mau se c

i i th h l h


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oi vi cac thc pham long nh nctng , nc mam, dau an thng ccha trong cac thung to , hoac be to thdung ong cao su sach , kho cam vao v trtren , di hay gia be e hut ra nen nhtrc khi lay mau phai khuay ky cho eu ,va bo i lt au va lt hai sau o mi

lay mau chnh thc cho vao dung cu ngmau.

- oi vi cac nguyen lieu va san phamthc pham the ran nh gao, bot, che,au..th lay mau phan tren, di , gia,ben canh cac bao hoac ong hang roi sauo tron eu cho ong nhat.-

Lng lng thc va thc pham toi


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Lng lng thc va thc pham toithieu can thiet e kiem nghiem

Tht va thc pham che bien : 250 500gCa, tom cua ca con : 250 500gTrng : 5 10 quaNc mam, nc tng, dam : 500 750mlDau m, Sa ti : 500 750mlRu cac loai : 750 -1000mlGao, bot, san pham che bie : 500750gBanh mt keo : 250 500 go hop, nv giai khat : 5 10 hopPham mau : 50 100g

II/ phan tch tai phong th nghiemM h i t h (


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-Mau phai c tron eu, xay nhuyen(neu la mau dang ran nh au phong,

gao)- Mau phai c ng trong bao b, co maso ten goi - Mau cho phan tch vi sinh phaic ng rieng vao tui, chai..a c vo

trung- Phai mo ta mau trc khi phan tch (phan tch cam quan mui, v, trang thai )

- Vao so mau : ten mau,ngay gi nhanmau, ch tieu can phan tch, thi gian traket qua.

Tien hanh kiem nghiem, neu trng hp

cha phan tch c ngay th can phai bao

NGUYEN TAC GI MAU


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Mau thc pham gi kiem nghiem , hoacc gi trong bao b ban au cua no ,hoac c ong goi trong ngng dung cukhong lam anh hng en chat lng thcphamTrng hp thc pham phai gi xa hoacmau co tranh chap phai ong goi ky phangoai co ong dau len nut buoc hoackep dau xi can than , tranh mau b anhtrao.Thc phan deb h hongth can phai gigap en phong kiem nghiemThc pham gi en phong kiem nghiemphai co phieu yeu cau kiem nghiem kem

C quan hoac nha may san xuat


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- Ngay va gi lay mau, ni lay mau- ngi lay mau

- yeu cau kiem nghiemBien ban lay mau can co:Ten ho c quan ngi lay mauTen ho a ch cua ngi co mau

Ngay gi lay mauLy do lay mauLoai hang va lng mauCh ky hai ben

Chu y : Phan mo ta mau . Mau kiem nghiemphai c gi lai 40% e lam oi chieu khi cokhieu nai , thi gian lu mau t 01 tuan en 03thang tuy theo tng loai mau bao quan

Chuan b mau cho phan tch


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Chuan b mau cho phan tch

Khi mau thc pham en phong th nghiem

Can phai tien hanh trnh t sau:

Kiem soat bao b co hp le khong

Kiem tra lai phieu gi kiem nghiem : ten

mau, ch tieu phan tch, ngay gi tra ketqua..

Vao so cua phong hoac kiem nghiemvien khi nhan mau

Tien hanh phan tch

Kiem nghien Hoa hoc gom 02 phan

- Cam quan

-

I / XAC NH HAM LNG NaCl


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I / XAC NH HAM LNG NaClCO TRONG THC PHAMPhng phap nh

lng trc tiep Phng phap Mohr1/ Nguyen tac cua phng phap Co hai phng phap xac nh ham lngNaCl trong thc pham :Nguyen tac da tren phan ng ket tuacua ion Ag vi ion Cl- trong moi trng trungtnh, vi ch th KCrO4 . Mot giot d AgNO3se ket hp vi CrO4-2 chuyen t mauvang sang mau o gach cua

NaCl + AgNO3 = AgCl + NaNO3 Ag+ + CrO42- = Ag2CrO4 mau o gach

2/ Cac e to ga anh hng c a


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2/ Cac yeu to gay anh hng cuaqua trnh phan ng

Trong mau phan tch khong c conguyen to nh Ba, Sr, cac halogenua F,Br, se gay ket tua cung vi K2CrO4cho ra mau o gach cuaMoi trng axt va kiem se lam tanket tua cua Ag2CrO4.Phai phan tch nhiet o thng ,

nhiet o cao se lam tan ket tuaAg2CrO4Dung dch chuan AgNO3 tranh anhsang mat tri

Hoa chat va dung cu


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Hoa chat va dung cu - AgNO3 0,1N

- Ch th K2CrO4 10%- NaOH 10%, HNO3 1:1Bnh tam giac

Pipet 10,20ml , Buret 10, 25mlX ly mauNeu mauthc pham dang ran thmau phai c nghien cho nhuyen ,tron euNeu mau dang long nh ncmam, nc tng..th mau phai c

lac ky va pha loang trc khi phan Tien hanh phan tch


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Tien hanh phan tch- Mau ran sau khi nghien can mot lng ng

vi o man cua muoi co trong mau t 1g- 20gcho vao bnh tam ga sau o cho them vao o100ml nc cat c un nong cho vao mau vaat tren may lac khoang 20 lay mau ra va,nh mc 100 ml sau o em loc

Lay 20ml t dch loc ( tuy thuoc vao lng NaClco trong mau e lay mot the tch thch hp cho

phan tch.) kiem tra lai pH co trung tnh hay khongbang giay th pH. Cho vao bnh tam giac 1mlK2CrO4 chuan o t t bang dung dch AgNO30,1N cho en khi xuat hien mau o gach benvng.

Tnh ket qua


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Tnh ket qua

NaCl% = Vm 0,00585g. 0,1N . F. V1. 100% V2 . g

0,00585g : he so g NaCl tng ng vi 1mlAgNO3 0,1N f : He so pha loangV1 : So ml AgNO3 tieu ton

V2 : So ml mau lay phan tchVm : the tch nh mc g : so gam mau lay phan tch

I / PHNG PHAP XAC NH NaCl


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BANG PHNG PHAP GIAN TIEP VOHARD

Nguyen tac Chuan o lng d cua AgNO3bang KSCN vi chth phen sat amoni ( NH4)2 SO4.Fe2(SO4)3. Mot giot dKSCN se ket hp vi Fe3+ cho mau o. Moitrng cua phan ng la moi trng axt

NaCl + AgNO3= AgCl + NaNO3 AgNO3 + KSCN = AgSCN + KNO3Dung cu va hoa chat- Bnh nh mc, pheu , Buret, pipet

HNO3, dung dch KSCN 0,1N, AgNO3 0,1NDung dch phen sat: ( NH4)2 SO4.Fe2(SO4)3 KOH 1N, AgNO3 0,1N

Chuan b mau th : oi vi mau co cac thanhh kh h th h h l


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phan m, am khac nhau th phng phap x lymau khac nhau: a/ Thc pham cha t beo < 5% : Can khoang 5 gmau thc pham a c nghien nat cho vao bnhtam giac cho them 200ml HNO3 4%lac trong 10-15.Sau o trung hoa = KOH 1N. Kh tap chat bang 5mldung dch kaliferoxyanua va 5ml Zn(CH3COO)2 nhmc len 250ml = nc cat. Lac eu va loc quagiay loc bang vang . Lay 20 hoac 25ml dch locva nh lng.b/ Thc pham cha nhieu chat beo > 5%Can mau vao khoang 1- 2g cho vao bnh tam

giac cho them 20mlKOH 1Nxa phong hoa .Chat beo se noi len tren mat. e nguoi vanh mc 100ml sau o loc. Lay 10 ml dch loccho them 2giot dung dch metyl da cam 0,5% vatrung hoa mau bang HNO3 6N sau o nh lng.

Lam mau trang song song

c/ Thc pham cha nhieu am ong vat


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Can khoang 1g mau tht a c xaynhuyen cho vao bnh nh mc 250ml cho t

nc cat co cha HNO3 tron eu vi mausau o cho them 10ml HNO3 am ac va20ml AgNO3 0,1N . un soi nhe va nho tnggiot KMnO4 bao hoa cho en khi khong mat

mau na. Lam mat mau KMnO4 bang vaigiot NaNO3 60% hay H2O2 . e nguoi va nhlng AgNO3 d bang KSCN 0,1N cho enmau hong gach

Tnh ket qua:% NaCl = 0,00585 ( Vt-Vm) 0,1N.Vm 100 m . Vm

II/ XAC NH O CHUA TRONG THC


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PHAMnh ngha : o chua bao gom : - Cac axt co trong thc pham. Cac axtnay hoac co san trong t nhien trong thcphamnh trai cay, axt hu c

- Axt cho vao thc pham vi muc ch chebien : Siro, nc chanh, cam nhan tao - Cac axt sinh ra trong qua trnh chuyen hoathc pham axt trong sa..

Do o xac nh o chua la xac nh ga trthc cua thc pham hoac la xac nh oh hong cua thc pham V du : sa, bot ,banh gao con tot hay a chua

Xac nh o chua bao gom :


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Xac nh o chua bao gom :

1/ Xac nh o axt toan phan 2/ Xac nh o axt de bay hi 3/ Xac nh o axt co nh

4/ Xac nh o axt t do cua daum 5/ nh tnh cac axt vo c ( t hoc)

6/ nh lng mot so axt hu c ( thoc)

1/ XAC NH O AXT TOAN


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/ C O OPHANnh ngha :

o axt toan phan la bao gom tat ca cacaxt co the nh lng bang mot dung dchkiem chuan. Cac axt nay chu yeu la cacaxt hu c: Axt axetic, malic, citric, tactric,

lacticbao gom cac axt khong bay hi vacac axt de bay hi. Cac axt cacbonic va SO2 di the t dohay ket hp eu khong tnh trong o chua

cua thc pham. Do o nhng thc phamnh bia, nc ngot co cha CO2 hoac SO2eu c loai tr , trc khi chuan o exac nh o chua

Ch th mau


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Hau het cacaxt trong thc pham la axthu c cho nen la cac axt yeu va khi c

trung hoa chung la bang baz manh nhNaOH, KOH. iem tng ng th pH bao gicung > 7 do o co the s dungphenolphtalein chuyen mau pH = 8,2 .

Cung co the s dung cac ch th :Bromotymol xanh, metyl o pH tai d8iemtng ng la gan bang 7.Nguyen tac : Xac nh o chua toan phan

cua thc pham la dung mot kiem chuanNaOH hay KOH e trung hoa het cac axttrong thc pham vi phenolphtalein lam chth. Chuyen t khong mau sang mau hong

Dung cu va hoa chat


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NaOH hoac KOH : 0,1N Dung dch phenolphtalein 1% pha trong con900.Buret, Pipet, can 0,0001gTien hanh th nghiem : Can chnh xac

khoang 10g thc pham a c nghien nhocho vao bnh tam giac, them nc catkhoang 30ml cho vao may lac khoang 1hsau o lay ra cho vao bnh nh mc 50ml,trang bnh tam giac = nc cat cho themvao bnh nh mc en vach. e lang sauo dung pipet lay ra 25ml dch trong chovao bnh tam giac e nh lng. Neu thc pham la chat long th lay V ml

Cho vao bnh non co cha san 25ml mau 5giotphenolphtalein chuan o t t dung dch NaOH 0 1N


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phenolphtalein chuan o t t dung dch NaOH 0,1Ncho en khi dung dch co mau hong nhat benvng.

Tnh ket qua: o chua ( mllg/g) = K. VNaOH. 50.N 25 .mK : he so cua loai axtN : nong o ng lng cua NaOHm : lng can mauTuy theo loai thc pham ket qua se bieu thbang mot so loai axt sau: K axt lactic = 0,09 ( Sa) K axt acetic = 0,06(dam)Cac loai trai cay: Vi dau m : K axt malic = 0,076 K axt oleic = 0,282 K axt citric = 0,064 K axt tactric = 0,075

2/ Xac nh o axt de bay hi


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2/ Xac nh o axt de bay hinh ngha : o axt de bay hi bao gom

cac axt thuoc nhom axt axetic : HCOOH,CH3COOH, C2H5COOH, C3H7COOH didang t do hoac di dang muoi.

Cac axt sau: axt lactic, CO2, SO2 khong tnhvao o axt bay hi.Nguyen tac : Dung mot nguon hi ncnong i qua thc pham, keo cac xt bay hi

khi gap lanh cac axt bay hi nay ngng tu laichay vao bnh hng va c chuan obang dung dch kiem vi ch th laphenolphtalein

Dung cu va hoa chatDung cu cat axt de bay hi


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- Dung cu cat axt de bay hi- dung dch chuan NaOH 0,1N

-Phenolphtalein 1% trong con 900

- Can 0,0001g- Buret, Pipet, bnh nonTien hanh th

Can chnh xac t 10 20g mau cho vao ong ngmau them vao ong khoang 50ml nc cat. atong vao he cat . Cho hi nc nong suc qua ongung mau va un nhe he cat. Hi thoat ra chayqua ong sinh han c lam lanh va chay xuong

bnh hng. Cat khoang chng 300ml dch thu cth ngng . Lay bnh non ra un nhe cho bay hi hetCO2 cho them 5 giot phenolphtalein va chuan obang NaOH 0,1N en khi xuat hien mau hong benvng.

Tnh ket qua : Tnh theo o bay hi cua axt


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axetc

Axt % = VNaOH . 0,1N. 0,06 .100

m (g)

Loai bo SO2 co trong mau hoac trong nccat

Sau khi nh lng axt de bay hi bang NaOHvi ch th Phenolphatalein cho them vaodch cat 1 got HCl tinh khiet, 2ml ho tinhbot, 1 hat tinh the KI va chuan SO2 t do

bang dung dch iot 0,01N ( V1). Cho them 28mlnatri borat bao hoa dung dch chuyen thanhmau hong nhat chuan o SO2ket hp

bang dung dch Iot 0 01N cho en mau xanh

Tnh ket qua :


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et quaTnh so ml NaOH thc te dung e nh lng axt

de bay hi: VNaOH = ( VNaOH - V1 - V2 )

10 10

Trong o : VNaOH : so ml chuan o cho axt de bayhi

V1 : so ml iot 0,01N s dung e nh lng SO2 t

doV2 : so ml ot 0,01N s dung e nh lng SO2ket hp

Co the tnh o axt de bay hi bang cach :

3/ Xac nh o axt co nh


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Nguyen tac : o axt co nh bao

gom tat ca cac axt khong bay hi.Sau khi mu c co can tren bepcach thuy e cac axt de bay boc

het. Can c hoa tan vao nc catva nh mc sau o lay ra chuan ovi baz NaOH 0,1 vi ch th

phenolphtalein.Dung cu va hoa chat: Bep cachthuy

Dung dch chuan NaOH hoac KOH 0 1N Tien hanh th nghiem:


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e a t g eCan chnh xac khoang 10 -15g thc pham mau chovao coc thuy tinh chu nhiet cho them t nc vao

mau e mau dang set ( neu mau long th khongcan cho them nc )at coc len bep cach thuythnh thoang khuay eu un en can. Lay mau rae nguoi sau hoa tan can bang nc cat nh mc100ml . Roi lay ra 50ml chuan o vi NaOH 0,1N

Tnh ket qua :Axt co nh mllg /g = 0,1N . Vm .VNaOH .K. m 50Vm : the tch bnh nh mcVNaOH : So ml NaOH tieu ton trong chuan oK : he so chuyen oi ra axt cu them : So lng gam mau lay phan tch50: so ml mau hut ra e phan tch


104/200

Hoac co the tnh nh sau:

Axt co nh mllg/g = K ( V1 V2 ) .N. mV1 : So ml NaOH 0,1N e nh lng

axt toan phanV2 : So ml NaOH 0,1N e nh lngaxt de bay hi

K : he so chuyen oi ra axt cu the

4/ o axt t do cua dau m


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Nguyen tac :Dau m e lau b thuy phan vacho ra cac axt beo t do. Cac axt t do nay c

chuan o bang dung dch KOH trong con moitrng ete-con o chua t do c bieu th bang ch so ochua ngha la so mgKOH can thiet e trung hoacac axt t do trong 1g dau m.Hoa chat va dung cu:Ete : 1 the tchCon : 1 The tch , ete : Con theo ty le 1:1Pha dung dch KOH 0,1N trong con 950 nh sau:Can 35gKOH trong 20ml nc cat , cho them concho u 1l. ng trong chai mau nau va e 21-48gi. Loc qua bong loc thuy tinh.

Kiem tra lai nong o KOH bang dungdch HCl 1N vi ch th phenolphtalein


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dch HCl 1N vi ch th phenolphtaleinva ieu chng dung dch KOH 0,5N

bang con. Muon co dung dch KOH0,1N pha loang t dung dch KOH 0,5N .Lu y: Dung dch KOH trong con phaic xac d8nh lai nong o trc 1-2ngay .Dung dch KOH 0,5N s dung cho nhlng o axt t do trong chat beo

cong nghiep. Dung dch KOH 0,1N s dung cho nhlng o axt t do trong chat beo thc

pham co o axt thap

Tien hanh th nghiem


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e a t g e Cho vao bnh tam giac 250ml , 150ml

dung dch hon hp conete , cho themvao 5 giot phenolphtalein ( neu trnghp dung dch tren khong co mau th

nho them tng giot KOH 0,1N trongcon en khi mau hong xuat hien.Can chnh xac khoang 10g chat beovao bnh tam giac khac hoa tan maubang dung dch ete-con 20ml vachuan o bang dung dch KOH 0,1Nch th phenolphtalein cho en mau

hon Tnh ket qua :o axt t cua dau m tnh theo %

% X K V N 100


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%X dau m = K .VKOH. N. 100 m

K : he so tnh ra cac loai axt beo, Neu la dau co Kaxt palmitic = 0,256, K axt oleic = 0,282Ch so o chua ( so mg KOH dung e trung hoa 1gdau m) tnh bang cong thc I

a

= 5,611. VKOH m

5,611: so mg KOH trong 1 ml KOH 0,1NVKOH so ml KOH 0,1N s dung e chuan o mau thm : so lng g mau em phan tchLu y : Neu mau la chat beo co nc ket quaphai tnh tren chat kho

5/ Phan tch protit (protein)


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p (p )nh ngha: Ve phng dien hoa hoc ,

protit la nhng chat hu c ma thanhphan cau tao gom C, H, O va N co khitrong thanh phan con co them S, P

Protit bao gom cac axt amin va nhnghp chat ( peptit, protein) khi thuy phancho 1 hay nhieu loai axt amin . Cong thc

chung cua cac axt amin NH2CHRCOOH.

Peptit la do mot so axt amin ket hp vi


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p pnhau bi day noi Peptit. Nhom chc cuaaxt amin nay ket hp vi nhom chc cua

axt amin kiaR CH CO OH + HNHCHR NH2 COOHProtein la nhng protit khac ( khong coday noi peptit) chia thanh holoprotein khi thuyphan cho cac axt amin va heteroprotein.Thanh phan chnh cua protein la cac

amino axtngoai axt amin con cho nhng chat khongphai la protit goi la chat phi protitV du nh Alcaloit

PROTIT THO


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nh ngha: Protit tho trong thcpham c

nh lng bang cach xac nh lng Nittoan phan va ket qua nhan vi 6,25. Nhvay protit luon co cha 16% la Nit. Thcte trong thc pham luon co ham lng nitcao hn 16% v co cac ni t khac trong thanhphan nh: alcaloit, amoniac, axt nitricNhng protit thc vat th ham lng nit < 16%.

% Protit = % N .FF : he soe chuyen oi t N sang Protit

Thc pham % N He so FHon hp 16 6 25


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Hon hp 16 6,25Tht 16 6,25Bap 16 6,25Sa va san pham sa : 15,66 6,38Bot my 17,54 5,7TRng 14,97 6,68au nanh 17,51 5,71Gao 16,81 5,95Thc an gia suc 6,25

Cacphng phap xac nh


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ProteinHien nay co nhieu phng phape xac

nh protit thc chat la xac nh ham lngNit . Phng phap chon phu thuoc vao oung o chnh xac cua phng phap vaieu kien san co cua phong th nghiem .

Mot so phng phap e nh lng Ni t nhsau: - Phng phap kjeldahl - Phng phap chng cat trc tiep

- Phng phap gia nhiet ( ot nhiet ocao)- Phng phap chuan o Formol- Phng phap phan tch quang pho


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NH + H SO ( NH ) SO


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NH3 + H2SO4 ( NH4)2SO4Lng d H2SO4 + NaOH Na2SO4 + H2O

Hoa chat va dung cuBnh Kendan, bnh tam giac, bo ch catH2SO4 am ac d=1,84Hon hp cac nhom chat xuc tac :

K2SO4, : 1000g K2SO4, : 50g CuSO4, : 30 g CuSO4, : 3,5g Selen : 30g K2SO4, : 100g K2SO4, :100g CuSO4, : 10 g CuSO4, :10 g Selen : 1g HgO :30g

NaOH : 50% khong cha cacbonat, HCl0 1N


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0,1NCh th mau: metyl o 0,016g + 0,083gbromocresol xanh nh mc thanh 100mlbang ethanol 96%u iem cua phng phap:

- Phng phap nay dung e xac nhtat caNi t cac dang co the chuyen

thanh amonium sulfat - Nitrat , nitric va hp chat nitrosokhong the chuyen thanh dangamonium sulfat bang phng phap nay

Tien hanh th nghiemCan chnh xac khoang 1g mau cho vao Kj ld hl ( kh i l l


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ong Kjeldahl ( khoi lng mau lay can nencha khoang 0,03g nitrogen) . Them vao

ong 25ml H2SO4 am ac them 10g honhp xuc tac va cho vao bep pha mau (he thong bep cua hang Foss) luc aupha cham e tranh trao ra . Sau khi mau

a tr nen xanh trong tiep tuc un them 45. e nguoi them vao ong khoang 100200ml nc, e nguoi chuyen toan bo honhp tren vao ong cat mau. Them 80

85ml NaOH 50% vao he thong cat chu ykhong lam thoat amoniac. Chuan b bnhhng co san 25 100ml HCl 0,1N vi vaigiot metyl o e hap thu amoniac . Khi dungdch khong chuyen mau na va lng dung

Trong qua trnh cat neu dung dch hngchuyen sang mau vang cua kiem th cho


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chuyen sang mau vang cua kiem th chothem axt HCl 0,1N vao bnh hng( hoac

dung 50ml dung dch axt boric 2% ) Chuano lng d HCl bang dung NaOH 0,1N. Tienhanh lam mau trang song songTnh ket qua

% N = 14 . (V1 V2 ) . 0,1 .100 1000 . mV1 : The tch NaOH 0,1N cua mau trangV

2: The tch NaOH 0,1N cua mau th

m : khoi lng mau lay phan tch% protein tho : % N x 6,25

MAY PHA MAU AM BANGPP KJELDAHL


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PP.KJELDAHL

MAY CHNG CAT AM


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Phng phapxac nh


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protein bang chng cat trc

tiepNguyen tac : ay la phng phap datren phng phap Kjeldahl co sa oi. etranh s mat amoniac trong qua trnh phanhuy mau bang axt manh va xuc tac thphng phap nay phan huy mau bang

kiem manh nh NaOH va Na2SO4 .Amoniacthoat ra c hap thu trong bnh co san axtboric va aminiac chuyen thanh ammoniumborate va chuan o lng d cua axt boricbang NaOH 0,1N .Phan tep theo lam giong nh KjeldahlTuy nhien phng phap nay khong cchnh xac nh phng phap tren va tietkiem c thi gian pha mau

Xac nh Protein bang phngh t


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phap otPhng phap nay c xay dng t nam1830 bi ong Dumas.Nguyen tac : Da tren phan ng o mauphan tch nhiet o cao khoang 9500C. Vi

kh ot la kh oxy. Kh mang la kh helium ( He).Ket qua c tnh ngay tren thiet b la Nitsau o tuy theo oi tng mau nhen vi heso e chuyen ve protein

Dung cu va hoa chatThiet b may phan tch , can giay goi mau,ong goi mau , Cu

Tien hanh phan tch:Mau can chnh xac khoang 0,2g neu maula chat long lay khoang 1ml Mau ran


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la chat long lay khoang 1ml. Mau ranc goi trong giay thiec, mau long th

ng trong ong bang thiec. Mau c atvao trong autosampler sau o dung kh nenay mau vao lo nung. ay lo nungc ot nong bang kh oxy len en 9500C.

Mau se chuyen thanh dang kh mau cchuyen qua ong loc e gi lai cac khkhong can thiet nh HCl, SO2. Kh con laibao gom CO2, Nox c kh mang He chuyen i

tiep vao buong mau o may t ongtrch ra 3mm3 kh cho i qua mot he thong loctiep o co san bay va co bot Cu tinhkhiet se hap thu mau kh va kh CO2 vaNO

Xthanh Ni t t do i vao au do va t

Phng trnh phan ng


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Phng trnh phan ng

NOx+ Cu CuO + N2

Tnh ket qua : % Protein = % N x 6,25

May phan tch Nit - Phng phap Dumas


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CHUAN O PHC CHAT


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Trong phan tch the tch chung ta co the sdung cac phan ng hoa hoc thoa mannhng ieu kien sau:1/ Chat tham gia phan ng phai phan ng

theo ty le nh lng nhat nh ( ty le hpthc)2/ Phan ng gia chat can xac nh vi

dung dch chuan ( dung dch chuan o) cua

thuoc th phai xay ra nhanh va hoan toan3/ cac chat la co mat trong san pham

nghien cu cung vi ch tieu can xac nhkhong can tr s chuan o chat can xac

nh

5/ Phan ng phai co kha nang xay ra nhiet o phong


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p g6/ S chuan o phai khong co phan ng

phu kem theo gay sai lech ket qua

Neu 6 iem neu tren ap ng c thnhan biet iem cuoi cua chuan o ( Tcla iem tng ng ) bang cach oi mauchat ch th , hoac dung ien cc ch th,hoac o o dan ienTuy nhien co nhieu phan ng khong thoaman cac ieu kien tren hoac thoa man

nhng phan ng khong ben b thay oinhanh mau cua ch th kho nhan bietc iem cuoi cua chuan o do vay phainghien cu phng phap mi o la :

Chuan o bang dung dch chat tao

V du : muon xac nh cac cation kim loainh Ca Mg Al co trong cac mau thc


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nh Ca, Mg, Alco trong cac mau thcpham th khong the s dung phng phap

chuan o axt baz, hoac co the s dungc bang phng phap ket tua nhng tonthi gian, hoa chat, nhan cong va cokha nang ket qua cha c chnh xac.Dung phng phap tao phc co the nhlng c cac cation khac nhau va cacanion

Phng phap tao phc: Phng phap taophc da tren viec dung cac phan ngtao thanh cac phc chat tan hoac cacmuoi t phan ly

+ + - - -

S lien quangia phng phap ket tuava ph

ng phap tap phc


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Phng phap ket tua lien quan chat chevi phng phap tao phc v nhieu phanng ket tua kem theo s tao phc con stao phc phai keo theo s ket tua cuachat kho tanV du:, [AgCl2]- ion phc tao thanh, khi d

mot giot Ag len [AgCl2]-

th AgCl ket tua

AgCN ket tua, [Ag(CN)2]- ion phc tao thanhkhi cho lng d Ag+ tac dung vi [Ag(CN)2]-

th se tao thanh ket tua AgCN.Phan ng tao phc se cho ra san phamcac muoi kem phan ly thanh cac ion:HgCl2, Hg(CN)2, Hg(SCN)2..

Mot trong nhng phng phap chuan o phcchat quan trong o la phng phap COMPLEXON


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q g p g p p. Hien nay trong chuan o complexon hau het

dung cac axt aminopolycarboxylic lam chat taophc , trong o etylendiamintetraaxetic (EDTA)chiem v tr quan trong nhat. Anion cua EDTA cothe tao thanh cac vong cang nam canh vi ion

kim loaiKhai niem ve Complexon :

Cac hp chat hu c la dan xuat cua axt

aminopolycarboxylic thng c goi la caccomplexon.

Complexon n gian nhat la axt Nitrolotriaxetic(NTA complexon I H3Y)

Cong thc cau taocua H3Y


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CH2COOH CH2COOH N CH2COOH hay H N+ CH2COO-

CH2COOH CH2COOH

Co ga tr hn ca la axt Etylendiamintetraaxetic (EDTA, complexon II H4Y)

HOOCCH2 CH2COOH N - CH2 CH2 N HOOCCH2 CH2COOH

Hay

HOOCCH2 CH2COO

H N+ - CH2 CH2 N+ H

- OOCCH2 CH2COOH

Complexon co cac nhom cacboxyl ( - COOH )cha Nit amin (N) nh cau tao nh vay


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nen hp chat co kha nang tao thanh

cung mot luc mot so lien ket phoi tr viion kim loai tap phc. Trong thc te thng dung muoi dinatricua axt etylendiamintetra axetic( EDTA, Ha-

EDTA complexon III hay trilon B viet tatNa2H2Y)

HOOCCH2

CH2COOH

N - CH2 CH2 N

Phan ng cua comlexon vi cac ion kimloai tao phc xay ra theo theo ty le hpphc ng lng nghiem ngat ieu o


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phc ng lng nghiem ngat. ieu oa m ra kha nang to ln cho viec dung

complexon e nh lng nhieu cation nh Ca,Mg, Zn, Cu, Al

Cac ac iem ac trng cua complexon

1/De dang phan ng vi nhieu kim loaitrong o co cation kiem tho la khong taophc vi cac chat tao phc khac ) taothanh cac phc ben tan trong nc

2/ Tan tot trong nc va cac dung moihu c

3/ Co mot so tac dung chon loc oi vi

ion nay hay ion khac


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S dung phng phap EDTA va cac

complexon khac e che cac kim loaikiem , kiem tho , kim loai nang khichung ngan can viec xac cac ion

khac. Vi tnh chat nay complexoncon c dung lam chat che.V du: S dung EDTA tao phc vicac ion kim loai khac co trong mau khican xac nh Be bang phng phapchuan o, o mau

Chuan o Complexon


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Phng phap complexon la phng phap phan tch chuan o datren viec dung phan ng cua ion kim loai tao phc vi caccomplexon, tao thanh cac muoi noi phc ( vong cang) ben, tphan ly, tan trong nc

Khi chuan o cac muoi kim loai tao phc bang EDTA xay ra cacphan ng sau trong giai oan ket thucNa2H2Y 2Na+ + H2Y2-

Me2+ + H2Y2- MeY2- + 2H+

Me3+ + H2Y2- MeY2- + 2H+

Me4+ + H2Y2- MeY2- + 2H+

theo cac phng trnh tren cho thay 1mol cation phan ng vi 1 molNa- EDTA ma khong phu thuoc vao hoa tr cua no .

Xac nh iem tng ng cua chuano complexon nh cac chat ch th la


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o complexon nh cac chat ch th lacac pham mau hu c tao vi cac

cation phc chat co mau cac chat chth kim loai

Khi chuan o bang EDTA cac hp chatmau nay dan dan se b phan huy dos tao thanh hp chat noi phc miben hn cua cation vi complexon. iem tng ng mau au tien cuaphc chat tao thanh t kim loai can xacnh vi chat ch th , sau bien mat vaxuat hien mau cua ban than cua chth t do

CHAT CH THT h h h l h t h


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Trongphng phap chuan o complexon chat chth la cac chat mau hu c :Crom xanh en axt, Eriocrom Tencac chat ch thnay trong moi trng kiem co mau xanh . Cac ionCa, Mg va nhieu ion khac tao vi chat ch th comau o nho. Khi chuan o vi EDTA th cac ionkim loai se tach ra khoi ch th va tao phc benvi EDTA va cho en khi ion kim loai tao phc benhoan toan vi EDTA th chat ch th tr ve trangthai t do , mau ban au cua ch th.Me2+ + HInd2- MeInd- + H+

xanh o MeInd- + Na2H2Y + OH

- Na2MeY + HInd2- + H2O

Cac loai phan ng c dungkhi chuan o Complexon


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khi chuan o Complexon

1/Phan ng tac dung trc tiepcua ion kim loai taophc vi complexonPhng phap chuan o trc tiepCach chuan o nay c dung e chuan o nhngion kim loai khi chuan o thoa man ay u cac ieu

kien cua phan ng chuan o the tchNguyen tac : Dung dung dch chuan EDTA trong moitrng kiem vi chat ch th eriocrom T en hay trongmoi trng axt vi ch th la xylen da cam. Trc khichuan o a dung dch phan tch ve ga tr pH xacnh sau o dung dung dch em a vao dung dchphan tch e gi cho pH khong thay oi. oi khi avao dung dch tac nhan tao phc nh tactrat,xitratmuc ch nhng chat nay lien ket vi mot so

cation gi cac cation nay trang thai khong ket tua

V du: Phan ng Ca vi Na2H2Y trongmoi trng kiem KOH pH = 13-14 vi


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moi trng kiem KOH pH = 13-14 vich th mau huynh quang fluorexonchuyen t mau huynh quang sangmau hongCa2+ + H2Y- CaY2- + 2H+

2/Phng phap chuan ongc Ch


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ngcChuan o ngc c s

dung khi : - khong co ch th thch hp oi viion can xac nh

- Cac ion tao thanh ket tua trongdung dch em- phan ng xay ra cham

- Xac nh ham lng cation trong cacket tua khong tan trong nc: Ca2+trong CaC2O4, Mg2+ trong MgNH4PO4, Pb2+

trong PbSO4

2/Phng phap chuan ongc


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ngc :Nguyen tac : Them vao dung dchphan tch mot the tch chnh xac dungdch chuan Complexon , un en soi

dung dch e thc hien phan ng taophc , sau o lam lanh va chuan lailng complexon d bang dung dchchuan muoi kim loai nh :ZnSO4 , MgSO4, Fe2SO3e xac nhiem tng ng dung ch th kim loaiphan ng vi ion magie, hay kem

V du: Xac nh nhom (Al) pH = 5, emaxetat khi o them mot lng d complexon


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vao dung dch phan tch sau o chuan o

lng d bang dung dch chuan o pH = 5Al3+ + Na2H2Y AlY- + 2H+ + (n-1) H2Y2-lng d

pH = 10( n-1)Zn2+ + (n-1) H2Y2- (n-1)ZnY2- + 2H+

Lu y : Khi cho complexon vao mau trong maua co san ch th Xylen da cam ma co mauhong th nh vay lng complexon la thieuphai cho them e dung dch chuyen ve mauvang ( iem tng ng t vang hong)

3/ Phng phap chuan o chat thePh h d t ti t


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:Phng phap da tren c s cation tao

phc vi complexon kem ben hn lacation can xac nh , va xay ra phanng trao oi cation kem ben o se

c gai phong va cation can phan tchse the vao v tr cua cation o. Chuano cation c giai phong ra vi EDTA. V du: Can phan tch cation Thori ( Th4+).Cho trc vao dung dch mot lngcomplexonat magie MgY2- . Sau o chuano lai lng ion Mg2+ tach ra bang dung

Phng trnh phan ng xay ra nh sau:


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Phng trnh phan ng xay ra nh sau:

pH =2Th4+ + MgY2- ThY + Mg2+ (a)Mg2+ + H2Y2- MgY2- + 2H+ (b)

V Th tao phc vi complexon ben hnMg , nen can bang chuyen dch veben phaiKet thuc chuan o , chuan o lai ion

Mg bang EDTA vi ch th Eriocrom Ten th co the tnh c ion Th co trongdung dch phan tch

4/Phan ng chuan o axtbaz : Trong qua trnh tng tac cua phan ng


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Trong qua trnh tng tac cua phan ngcomplexon vi cation nao o lam tach motlng tng ng ion Hydro. Chuan o lailng ion hydro c tao thanh bang motdung dch kiem chuan manh vi chat ch

th axt-baz hay bang phng phap iot Me2+ + H2Y2- MeY2- + 2H+

2H+ + 2OH- 2H2O ch th metyl o

3Me2+ +3H2Y2-+ IO3-+ 5I-3MeY2-+ 3H

2O+ 3I

2Iot tach ra c chuan lai bang thiosunfat

S2O32- + 3I2 3 S4O62- + 6I-

CHUAN O HON HP NHIEU ION CAC CHAT CHE

T il B t h i hi i ki l i d


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Trilon B tap phc c vi nhieu ion kim loai do

o muon chuan o mot ion kim loai ta phaitnm ieu kien thch hp e ch cation canxac nh phan ng vi trilon B , con cac ionla khong phan ng.

Chat che phai thoa man cac ieu kiensau:Chat che khong tao phc vi cation can xacnh, hoac tao phc kem ben hn phc

complexonat cua chung- Cac chat che thng dung: KCN dung e che Fe, Cd, Hg, Cu, Zn, Ag, Ni,Co

C s ly thuyet cua phng phapcomplexon


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Cau tao cua muoi noi phc c taothanhAxt Etylendiamintetraaxetc ( EDTA) la mot axtbac 4 co 4 ion hydro linh ong va hainguyen t nit vi tnh chat c ban la co 6nguyen t co the tham gia phoi tr khi taothanh cac vong 5 cua hp chat noi phcV du: ong glicocoliat

0 = C -----O O ------C = O Cu

H2C ----H2N NH2----CH2____

Trong moi trng hp muoi noi phc ctao thanh khi cac ion kim loai tao phc thecac nguyen t hydro hoat ong cua nhom


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cac nguyen t hydro hoat ong cua nhomchc hu c , mat khac tac dung vi cacnhom nao o tao nen lien ket phoi tr. Cac nhom co ion hydro co kha nang bion kim loai the va tng tac vi ion kim loaitao phc bang lien ket chnh la nhomcarboxyl- COOH, nhom sunfoxilic SO3H, hydroxytOH

HOOCCH2 CH2COOH N - CH2 CH2 NHOOCCH2 CH2COOH

Muoi noi phc vi EDTA tao thanh motmat la do s the cac nguyen t hydro hoatong cua nhom caboxyl tao phc ay


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ong cua nhom caboxyl tao phc. ayEDTA ket hp vi ion kim loai tao phc

bang hoa tr chnh mat khac do s tngtac cua nguyen t Nit co kha nang taolien ket phu ( phoi tr) vi ion kim loi taophc

V du : muoi noi phc cua Canxi ( Na2CaY) O=C----O O----C=O

H2C Ca CH2

N N

NaOOCCH2 CH2 ---CH2 CH2COONa

Xac nh o chuan cua dungdch EDTAPh d d h h EDTA d i di t i


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dch EDTAPha dungdch chuan EDTA s dung muoi dinatri

cua axt etilendiamintetraaxeticNa2C18H14O8N2 . 2H2O, muoi c say 1201400C trong 2 g se tr thanh muoi khan. Sauo lay ra e nguoi va can pha chuan.

MEDTA = 372,24g, 1MEDTA = 372,24g/ 1l dung dch1 N EDTA = MEDTA / 2 = 186,12/ 1l dung dch

Xac nh o chuan cua EDTA bang ZnO,

CaCO3, Zn kim loai tinh khiet hoa hoc , hoacong chuan phicxenan nh muoi magie sulphat0,1N, ),05N..

XAC NH HAM LNG CAN XI( Ca)

X h C hi h h


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( Ca)Xac nh Ca co nhieu phng phap :

- PP. trong lng CaC2O4 can dangCaCO3 hoac CaO- PP ket tua dang CaSO4-PP Chuan o : Ca ket tua CaC2O4 sau o

nh lng bang phng phap KMnO4- Phng phap complexonCac nhc iem cua phng phap:Thi gian lau, ket tua Ca b ket tua co

nhieu tap dan en ket qua nh lngkhong chnh xac cho nen hien nay sdung phng phap Complexon la hieu quava chnh xac nhat

Xac nh Ca bang phng phap complexon

Nguyen tac: Da tren chuan o trc tiep


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Nguyen tac: Da tren chuan o trc tiepion Ca bang dung dch chuan EDTA trong moitrng kiem manh pH 12 14 vi chat chth la murexit hay crom xanh en axt.

Cach xac nh :

Dung pipet lay 25ml dung dch Ca2+ cho vaobnh tam giac. Trung hoa dung dch bangNaOH sau o cho them 5 ml NaOH 20% echo pH cua dung dch 12-14, cho them vai

hat murext lac eu. Tien hanh chuan onhanh bang dung dch EDTA en khi maucua dung dch oi t xanh sang tm.


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BAN CHATVA PHAN LOAI CACPHNG PHAP OXY HOA KH


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nh ngha : Phan ng oxy hoa kh la phanng trong o co s thay oi so oxy hoa cuamot hoac vai nguyen to Chat oxy hoa la chat cha nguyen to nhanelectron.Chat kh la chat cha nguyen to choelectron.V du: Sn2+ + 2Fe3+ Sn4+ + 2Fe2+

Sn2+ -2e- Sn4+ (S oxy hoa)Sn2+: Chat kh Fe3+ + e-Fe2+ (s kh )Fe3+ : chat oxy hoa

Ban chat cua phng phap chuan o oxyhoa kh


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hoa kh

1, Xac nh cac chat can xac nh ma cos thay oi ve hoa tr cua cac chat o khiphan ng ket thuc

Fe2+ Fe3+

2/Cac thuoc th tng tac vi chat can xacnh theo ty le hp thc trong phan ng bthay oi hoa tr

Ca + C2O42-

CaC2O45CaC2O4 + 2MnO4- +16H+ 5Ca2+ + 10CO2+2Mn2+ +8H2O

o o phng phap chuan o oxy hoa kh

Y NGHA CUA PHNG PHAP OXYHOA KH

Phng phap c ng dung rong rai trong cac


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Phng phap c ng dung rong rai trong cacphong th nghiem . Phng phap cho phep xac nh

nhieu chat vo c va huu c, cac hp chat c kim ,cac chat sinh hoc va thc pham khac nhau .u iem cua phng phap- Cho o chnh xac cao

-o lap lai tot- n gian, t ton thi gian phan tch-Cho phep xac dnh cac chat de b oxy hoa hoackh va con co the xac nh cac chat khong boxy hoa hoac kh- S chuan o oxy hoa kh xac nh tai iemtng ng co the dung ch th va cung co thekhong dung ch th hoac dung cac phng phapdung cu

- S chuan o xy hoa cothe thchien tat ca moi trng


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g

-Co the tien hanh xac nh bangcac phng phap chuan o trc tiep,gan tiep va chuan o ngc.

Phan loai cac phng phap chuan ooxy hoa kh


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Da trenac tnh cua thuoc th c

ban ( dung dch chuan o c ban )c s dung cho tng trng hp cuthe e chuan o cac hp chat rieng

re hoac cac hp phan rieng bietcua hon hp chat can phan tch magoi ten phng phap. V du: Phng phap da tren s oxy

hoa cua Pemaganat goi la phngphap PemaganatPhng phap da tren s oxy hoa

i t i l h h I t

Phng phap da tren s oxy hoa


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Phng phap da tren s oxy hoa

cua Crom VI goi la phng Cromat- Phng phap da tren s kh cuaaxt Ascobic goi la phng phapascobic

Nguyen tac cua pp. chuan o oxy hoakhChuan o chat kh bang dung dch chuan


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Chuan o chat kh bang dung dch chuan

la chat oxy hoa , chuan o cac chat oxyhoa hoa th bang dung dch chuan la chatkh V du : Xac nh Fe2+ la chat kh vay

s dung chat chuan oxy hoa la KMnO4 Fe2+ + MnO4- Fe3+ + Mn2+

Kh cac hp chat co hoa tr cao xuonghoa tr thap bang cac chat kh manh

Cu2+ + Sn2+ Cu0 + Sn4+Thong thng trc tien kh chat oxyhoa can xac nh en hoa tr thap hnsau o chuan o bang dung dch chuan

CAC DUNG DCH CHUAN DUNG TRONGPHNG PHAP OXY HOA KH


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Cac dung dchchuan thng c su dung

cho phng phap nay : Cac dung dch chuanla cac chat oxy hoa manh : KMnO4,K2Cr2O7, KI, Kali Bromat..

Dung dch co cac chat kh manh :Na2S2O3, Axt ascobic , Hp chat cua Cr2+ cotnh kh manh

1/ Kali permaganat : KMnO4 trong moi

trng trung tnh, axt va kiem s thay oihoa tr cua Mn trong cac moi trng o

-Moi trng axt:

M O4-

+ 5 + H+

M2+

+ H2O + H+

- Moi trng kiem MnO4- + 3e + OH- MnO2+ OH-

Moi trng tr ng tnh


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- Moi trng trung tnh :

MnO4-

+ 3e + H+

MnO2

+ H2OMnO4

- + e- + OH- MnO42-KMnO4 : la mot trong nhng chat oxy hoa manhnhat E0KMnO4/Mn2+ = 1,52VPhan ng oxy hoa kh cua KMnO

4phu thuoc vao

moi trng e cho ra cac san pham khacnhau.e tang them toc o cua phan ng co chothem cac chat xuc tac nh muoi Mn, Fe, Cu e xac nh o chuan cua dung dch KMnO4

thng dung axt oxalic H2C2O4 , KI, muoi Mor (NH4)2Fe(SO4)2iem tng ng c xac nh bang d mot

giot KMnO4 cho dung dch mau hong

- Cac hp chat cua Mn3+ va Mn4+

chu yeu e chuan o cac hp chathu c


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hu c

Cac chat goc thng c dunge pha dung dch chuan la Mn3+ :Mn2(SO4).2Al2(SO4)3, , K2SO4.Mn2(SO4),

2/ Iod trong dung dch KIKI + I2 K(I3)I3 + 3e- 3I-

S dung dung dch Natri thiosunphatlam chat kh 2S2O32- + I3- S4O62- +3I-

Viec chuan o bang iot tien hanh trongmoi trng trung tnh hay trong cac dung dchem cacbonat photphat borat iem tng


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em cacbonat, photphat, boratiem tng

ng dung ch th ho tinh botPhng phap chuan o bang iod c sdung rong rai e o cac chat vo c vahu c

3/ Kali cromat KMnO4 , bicromat K2CrO7 , anhidriccromomic , kali bromat ( KBrO3) la cac chatoxy hoa manh S chuan o c thc hientrong moi trng axt.Tai iem tng ng

dung chat ch th hoac khong dung chthCac chat kh c s dung cho phngphap nay la cac kim loai t do, cac hp

h t F2+

S Oxy hoa va tng tac axtbaz


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baz

Khi them axt hoac baz vao he oxy hoakh co the gay ra s thay oi ac trngcua phng phap

V du : khi them axt vao he oxy hoa kh

cua AsO43- / AsO2- + I2/2I- xay ra s kh tAs5+ As3+

H3AsO4 + KI + 2HCl HAsO2 + I2 + 2H2O +KCl

Khi them kiem xay ra s oxy hoa As3+ As5+

AsO2- + I2 + 4OH- AsO43- + 2I- + 2 H2O

Hang so can bang cua phanng hoa kh


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Cac phan ng oxy hoa kh thuan nghch

. S can bang c thiet lap khi Eox bangEkh .V du :MnO4- + 5Fe2+ + 8H+ Mn2+ + 5Fe3+ + 4H2OOx1 Kh2 Kh1 Ox2Bieu thc cua L tac dung khoi lng( [Mn2+]/[MnO4-][H+]8 .([Fe3+]5 / [Fe2+]5+ = KMnO4-/

Fe2+ K:hang so can bang


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C S PHAN TCH TRONGLNG

ac iem cua phan tch trong lng


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ac iem cua phan tch trong lng

Phan tch trong lng la mot trongnhng phan tch quan trong nhat cuaphan tch nh lng: Phan tch nh

lng nc ng dung e xac nhthanh hoa hoc cua nhng oi tngnghien cu nh kim loai, silicat, vo c,

hu c..Phng phap xac nh trong lng coo chnh xac cao

BAN CHAT CUA PHAN TCH TRONGLNG

nh ngha: Phan tch trong lng la mot


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nh ngha: Phan tch trong lng la mot

phng phap cua phan tch hoa hoc nhlng da tren s o chnh xac khoi lngcua chat can xac nh hoac cua thanhphan no c tach ra trang thai tinh

khiet hoa hoc hoac di dang hp chatthch hp co thanh phan khong oi bietchnh xac.

S tach trc tiep chat can xac nhhoac cac thanh phan cua no ra khoi sanpham di dang tinh khi61t hoa hoc gapnhieu kho khan oi khi khong thc hien

d d h h k t t

Phng phap tach ket tua:Chuyen lng can mau thanh dangd d h th


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dung dch, them vao vao mau o

lng thuoc th thch hp, thuoc tho se phan ng vi chat can phantch thanh mot hp chat t tan. Khi o

hp phan cua chat can phan tch (cation , anion) c tach ra t dung dchdi dang ket tua thc te khong tan.Ket tua c tao thanh c loc

hoac ly tam, roi ra ket tua e loaitat ca nhng tap chat. Roi ket tuac say hoac nung en trong lngkhong oi va c can tren can

PHAN LOAI CAC PHNG PHAP PHAN

TCH TRONG LNG


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Chia lam 3 nhom ln :- Phng phap tach- phng phap ket tua

- Phng phap cat


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S o phan tach vang HP KIM


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HNO3 + HCl 1:3

Oxyhoa H2O2

Ra ket tua = HCl loang

Say, nung

Can Au tinh khiet

Cho dong ien mot chieu chay quadung dch (nc ra va nc loc) trong


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g ( ) g

ieu kien xac nhth Cu kim loai sec tach ra va bam tren catot Platintr oi vi dung dch

( va a c can trc) da vaolng can cua catot se suy ra hamlng cua Cu trong hp kim. phngphap ien trong lng

2/ PHNG PHAP KET TUA

Nguyen tac cua phng phap


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Ket tua nh lng cau t can phan tchbang cac phng phap hoa hoc di danghp chat hoa hoc t tan. Ket tua c tachrara say hoac em nung , khi o ket tuathng c chuyen thanh mot chat mi

co thanh phan biet chnh xac. Hp chatnay c can tren can phan tch.Phan biet dang ket tua va dang canDang ket tua: la dang chat can xac nhc ket tuaDang can: la dang chat can xac nhc canV du: khi xac nh ion SO42- bang phngphap trong lng , ket tua chung bang ion

2+

SO4

2- + Ba2+ = BaSO4Chat can X dang KT dang can


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Chat canX dang KT dang can

Trong mot so trng hp dang canva dang ket tua khac nhau2Fe3+ + OH- Fe(OH)3 Fe2O3Chat X dang KT dangcan

3/ Phng phap catNguyen tac : Chng cat nh lng cau t


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can xac nh di dang hp chat bay hi.Phan can tach ra bang cach ot nongmau phan tch hoac bang tac dung cuathuoc th thch hp lam giai phong ra sanpham bay hi. Co phng phap trc tiep va

gian tiep.

PP.Trc tiep: Cau t can phan tch cbay hi sau o hap thu vao chat hap thu

phu hp, da vao s tang khoi lng chathap thu ngi ta tnh c lng cau tcan xac nh

V du:Xac nh CO2 trong a cacbonat CaCO3 + H

+ CO2 + H2O CO2 + 2NaOH Na2CO3 + H2O


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CO2 + 2NaOH Na2CO3 + H2O

Mau Cacbonat c phan huy trong thiet bac biet trongmoi trng axt manhchophep giai phong ra CO2. . Ham lng CO2c hap thu vao hon hp dung dch

CaO+NaOH.PP.cat gian tiep : Trong phng phap nayla xac nh phan con lai cua chat sau khia tach hoan toan chat can xac

nh.Hieu so trc va sau khi cat chatcan xac nh ta se tnh c chat can xacnhV du: Tnh BaCl2.2H2O

B Cl 2H O kh B Cl + O

Nhng u iem va nhc iem cuaphng phap:


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phng phap:

- Xac nh o chnh xac cao at ti0,01 0,005% vt xa o chnh xac cuachuan o

- Xac nh c nhieu kim loai ( cation)va cac a kim ( anion), cac thanhphan cua hp kim, quang, silicat..-Nhc iem:- Keo dai thi gian, khong kinh te nhien tieu hao

Cach tnh toan trong phng phap tronglngTnh lng can cua chat phan tch:

a/ ket tua dang tinh the


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a/ ket tua dang tinh the

V du : xac nh CaCO3 co trong mau cacbonat CaCO3 + 2H+ Ca2+ + H2O + CO2 Ca2+ + C2O42- Ca2C2O4 + CO2 Ca2C2O4 nung t0C CaO + CO + CO2

Rut gon: CaCO3 Ca CaOTnh lc can phai can: MCaCO3 -----MCaO Xg -------0,5g Xg= 0,5x 100 = 0,9g

56Vay oi vi ket tua tinh the dang can ( ket tua)nen co la 0,5g

b/ Ket tua dang vo nh hnhnh:Fe(OH)3


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( )3

Khi nung len Fe(OH)3 Fe2O3Vay lng can dang ket tua nenla 0,1g

Cong thc tong quat: Ket tua tinh the : X = mMA.0,5/ nMA1Ket tua vo nh hnh : X = mMA. 0,1/

nMA1

KY THUAT PHAN TCH TRONG

LNG1/ Lay va hoa tan mau can


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/ y

Lng can cua chat phan tch cang ln,o chnh xac tng oi cua cac ket quaphan tch cang cao.- e tnh lng can can phai biet hamlng gan ung cua cau t- Lng can qua nho dan en sai socang ln- Sai so cho phep can khong c vtqua 0,1%

- S dung can co o chnh xac 0,0001g thlng can toi thieu co the can c vio chnh xac cho phep la 0,1%- Neu can 1g vi sai so 0,0001g th sai so

h h

- Neu can 0,1g sai so se la 0,1%

Nh vay lng can toi thieu khong ch h 0 1


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nho hn 0,1g

- Ham lng % cua chat can xac nhtrong mau cang nho th lng can canphai cang ln

2/ Lay mau can e phan tch- Lay mau can chnh xac ong vai tro quantrong trong phan tch nh lng.

- Tnh ung cua cac ket qua phan tchphu thuoc vao o chnh xac cua viec laymau can phan tch

- Neu mau la chat ran thng s dungcoc thuy tinh, thuyen can bang kim loai,giay bac


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S dung muong inox nho e lay mau- Neu mau la chat long th dung ongnho giot e lay mau va cho vao cocthuy tinh e can

- Neu mau la chat bay hi phai dung bnhnh mc nho co nut mai, hoac dung cuthuy tinh co nut mai e tranh bay hi cuamau.

Trng hp s dung ngay coc can e xly mau luon th tat ca dung cu lay mauphai c lam sach va say kho can tronglng khong trc sau o can mau . Hieu

t l l

Hoa tan lng can : Mau sau khi canchoa tan bang axt hoac nc cat trong cocth ti h h hi t h b b t h


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thuy tinh chu nhiet hoac bang bat s nhphai ay bang nap knh ong ho , emat lom quay xuong di.

Ky thuat ket tua

Phu thuoc vao chat nh ket tua dangnao th s dung thuoc th cho phu hp eket tua c hoan toan.

Lng dung moi : mau ran se c phaloang bang nc hoac hoa tan bang axt ,tnh toan lam sao cho dung dch thu c conong o khoang 0,1N

Nh vaytrong dung dch co cha 0,1 nglng gam chat can phan tch bang 1000ml The tch dung moi lat e hoa tan mause la:


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se la:

0,1g -------1000ml Xg -------Vml suy ra : Vml = 1000 a/0,1 = 100ml.Xg mauKet tua cac ket tua tinh the : cac ket tua c ket tua khi un nongdung dch tren bep ien hoac bep cachthuynhng khong c un soi. Thuoc thutao chat ket tua c nho t t va dung

u thuy tinh khuay nhe sau o e nguoiva lang ket tu. Nho them vai giot thuocth na neu khong thay tao ket tua thyen tam la ket tua a c hoan toan.

Ket tua cua cac ket tua vo nhhnhNh Fe(OH)3 Al(OH)3


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Nh Fe(OH)3,Al(OH)3

Ket tua cua cac ket tua vo nhhnh t dung dch nong, ac. Ket tuac tien hanh bang cach themnhanh chat ket tua e thu c ketco be mat nho nhat (tao bong cuctap trung khong phan tan trong dungdch)

Loc va ra ket tuaLoc : Trong phan tch nh lng dunggiay loc khong tro e loc ket tua


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CAC IEU KIEN TOI U E KETTUAieu kien ket tua dang tinh the

1/ Tien hanh ket tua t dung dch u


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1/ Tien hanh ket tua t dung dch u

loangbang dung dch thuoc th loang. Khi kettua t dung dch loang se ket tua c tinhthe ln hn2/Them chat ket tua vao t t theo tnggiot , neu cho vao nhanh se tao nhieu tamket tua lam cho tinh the ket tua b nhuyen3/ Khuay dung dch ket tua bang ua thuytinh e tranh s qua bao hoa theo vung vatang ket tua ln

4/ Tien hanh ket tua bang dung dch nongse lam tang s ket tua ln

ieu kien ket tua vo nh hnhCac ket tua vo nh hnh co khuynh


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hng hap phu va tao thanh dungdch keo, do vay ket vo nh hnh dung dch nong , ket tua t dung dchac khi o ket tua tao thanh de bco ac lai , de loc va de ra. Khiket tua xong nen them mot the tchln nc khoang 100ml muc ch cho

phan hap phu ket tua chuyen vaodung dch tuy nhien khong nen keodai va cho loc mau ngay

Cac phng phap tang o chnh xaccua phan tch trong lng

S i t h t k t t th


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-

S giam o tan cua chat ket tua:them

lng d thuoc th co cung ion cua chatket tua. Tuy nhien khong nen dung lngd chat ket tua qua ln se an en stao phc va lam tang o tan cua chat

ket tua V du : BaSO4 neu ket tua Ba2+ th themSO42- va muong ket tua SO42- th them ionBa2+

- Tm thuoc th ac trng cho phng phapmuon xac nh, loai bo cac yeu to gayanh hng en qua trnh cong ket kettua- Xac nh song song hai hoac ba mau e


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TNH TOAN LNG CANMNa2SO4 = 142,04 , MBaSO4 = 233,4

BaSO4co cau truc tinh thenen lng can


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4 g

dang ket tua khoang 0,5g , vay lng cancho Na2SO4 = 0,5.142/233,4 0,3g mauMau can va pha trong bnh nh mc en

vach.2/ Tnh lng BaCl2.2H2O cho vao mau eket tua BaCl2.2H2O + Na2SO4 BaSO4 + 2NaCl+ 2H2O 242,2 ----- 142 X 0,3g X = 0,5g1000 ml dung dch cha 121,1 BaCl2.2H2O

PHNG PHAP XAC NH SO4 TRONGTHC PHAM

Tnh ham lng SO4 co trong mau nc hoacthc pham co hai phng phap:


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thc pham co hai phng phap:

1/ Bang phng phap so mau

2/ Bang phng phap trong lng

Nguyen tac cua phng phap ket tua va

nungVi ham lng SO4 trong thc pham t 0,5%tr len th dung phng phap trong lngMau thc pham c xay nhuyen va cankhoang 10g mau vao chen s cho vao lonung nhiet o t 5500C 6000C.Dung H2SO4loang chuyen cac chat khoang ve dang

Tien hanh th :Mau thc pham c xay nhuyen va cankhoang 10g mau vao chen s at len


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bep ien than hoa mau sau o tro hoa chovao lo nung nhiet o t 5500C 6000Cnung trong 2gi cho en khi mau trang hoantoan. Lay mau ra e nguoi sau o hoa tant nc, dung HCl hoa tan mau cho tan hetva loc mau. S dung dch loc cho t tBaCl2 20% vao un nong nhe dung dch choen khi mau ket tua hoan toan . Lay cocmau ra e qua em, hom sau loc bang

giay loc bang xanh. Dung nc cat trangra ket tua nhieu lan cho en khi het Clorth bang dung dch AgNO3.

Giay loc cung chat ket tua c goi lai cho vaochen s nung loai nho at len bep ien than hoa,tro hoa trong lo nung nhiet o 5500C 6000Cnung trong 30 cho en khi mau trang hoan toan.Lay chen s ra cho vao bnh hut am e nguoi


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Lay chen s ra cho vao bnh hut am e nguoi

va can ket tua.

Tnh ket qua : BaSO4%= (G1 -G2 ).100.V.f m .VmG1 : Chen khong + mauG2 : Chen khongV: the tch bnh nh mcM : lng can

Vm : the tch hut mau % SO4 = %BaSO4 x MSO4 MBaSO4


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