เทคนิคการแยก Separation Techniques

Slide 1 Ksp Qsp
5.00 mL 0.015 M Ca(NO3)2 20.00 mL 0.050 M Na2SO4 CaSO4
Ca2+ (aq) + SO42- (aq) CaSO4 (s)
Ksp CaSO4 = [Ca2+][SO42-] = 2.4 x 10-5

= 1.2x10-4

A B P Ksp AP BP P A B
A (aq) + P (aq) AP (s)
B (aq) + P (aq) BP (s)
A B
Ksp (AP) << Ksp (BP)
Qsp (AP) > Ksp (AP)
Qsp (BP) < Ksp (BP)


Ksp Fe(OH)3 = [Fe3+][OH-]3 = 2 x 10–39
Ksp Mg(OH)2 = [Mg2+][OH-]2 = 7.1 x 10–12
Ksp Fe3+ Mg2+
≤ 1 ppt 0.10 M Fe3+
[Fe3+]left ≤ (1/1000) x 0.10 ≤ 1.0 x 10-4 M
Ksp = [Fe3+][OH-]3 = 2 x 10–39
2 x 10-39 = 1.0 x 10-4 x [OH-]3
[OH-]min = 3 x 10-12 pHmin = 2.5
Mg(OH)2
7.1 x 10-12 = 0.1 [OH-]2
[OH-]max = 8 x 10-6 M pHmax = 8.9
Fe3+ Mg2+ [OH-] [OH-]max Mg2+ [OH-]min Fe3+ 1 ppt ()
[OH-] 3 x 10-12 8 x 10-6 M pH 2.5 - 8.9
Separation Techniques 1

NH3/NH4
HOAc/NH4OAc
NaOH/Na2O
Zn2+, Al3+, Cr6+, V5+, U6+
Separation Techniques 1
2+ [S2-] 0.1 8 x 10-22 M `[S2-] pH
- Ka H2S Ksp MS
H2S(aq) + H2O(l) HS-(aq) + H3O+(aq) ;Ka1= 9.6 x10-8
HS-(aq) + H2O(l) S2-(aq) + H3O+(aq) ;Ka2= 1.3 x10-14
MS(s) M2+ + S2- [M2+] [S2-] = Ksp
Separation Techniques 1
Cd2+ Tl+ H2S 0.1 M
CdS (s) Cd2+ + S2- ; [Cd2+] [S2-] = 1 x 10-27
Tl2S (s) 2 Tl+ + S2- ; [Tl+]2 [S2-] = 6 x 10-22
CdS Ksp [S2-] CdS Tl2S
[S2-] CdS
[S2-] Tl2S
[H3O+] [S2-]
Separation Techniques 1
II: As3+ Sb3+ Sn4+
III: (NH4)2S 2
II: Fe3+ Al3+ Cr3+ Mn4+ ()
II: Mn2+ Ni2+ Co2+ Zn2+
IV:
Ca2+ Ba2+ Sr2+
V:



(org)
100 mL 200 200 mL 240
200 mL org
100 mL aq
2 A 200 + 67 = 267
100 mL org
100 mL aq
A 200
2
2302244 Anal Chem II
A 240
200 mL x 1
[A]i = A (aq phase) i
i =
[A]o = A (org phase) i

[A]o = A (org phase) i

2302244 Anal Chem II

K of I2 = 85 [I2] 50.0 mL 1.00 x 10-3 M I2 a) 50.0 mL, b) 2 x 25.0 mL, c) 5 x 10.0 mL
()
= Phase ratio; Vorg/Vaq
2302244 Anal Chem II
like dissolves like
KD
benzoic acid naphthalene dichloromethane (CH2Cl2) 5% NaOH NaHCO3 benzoic acid (CH2Cl2)
5% NaOH
dichloromethane (CH2Cl2)
pKa = 4.2
pKa ~ 10
dichloromethane (CH2Cl2)
p-chloroaniline benzoic acid ( pH < pKa 2 ~ 2) benzoic acid CH2Cl2
5% HCl
pKa = 4.6
pH > pKa 1.5
Separation Techniques 1
[HQ]org [M2+]aq
Separation Techniques 1


(absorption)
liquid-liquid extraction
Separation Techniques 1
sorbent
Male Luer tip fitting
2302244 Anal Chem II
sorbent compressed air N2
(centrifugation)
SPE Tube
SPE Disk