18 198, 203, 204, 207, 209, 212, 213.
18. 20,00 20,00 0,0200 / K2CrO4. Ag2CrO4 , , I. 24,60 0,0400 / Na2S2O3. Ag+ .
. :
2Ag+ + (.) = Ag2CrO4 ↓ (13)
2 + 6 I + 16 H+ D 2 Cr3+ + 3 I2 + 8 H2O (14)
2 + I2 D + 2 I (15)
Ag+ .
- (14) ,
+ 8 H+ 3ē = Cr3+ + 4 H2O → f()= 1/3.
(13) Ag+ , , 2 Ag+ 3 . Ag+ :
2 Ag+ 3 ē
1 Ag+ ē
x = z = 3/2. Ag+ 2/3.
:
(1/3K2CrO4) = 0,0200 / (1/3) = 0,0600 /;
(1Na2S2O3) = 0,0400 / 1 = 0,0400 /.
: 1) 6.3 ; 2) . .
K2CrO4, (13):
(14) 20,00 16,40 = 3,60 K2CrO4.
Ag+ . . . (2/3Ag+) = 71,912 /,
m(Ag2+) = 3,60 ∙ 103 ∙ 0,0600 ∙ 71,912 = 0,01553 ,
:
ρ*(Ag+) = 0,01553 /20 ∙ 103 = 0,7766 /.
19 225, 226, 230, 232, 234, 236, 243, 244.
19. Al2O3 , 1,0220 , 25,00 III [C(1/2 . III) = 0,2151 / ], 9,83 0,1015 / .
. :
Al3+ + H2Y2 D AlY + 2 H+
H2Y2 + Zn2+ D ZnY2 + 2 H+
(. 6.3). Al3+ :
n(1/2 Al3+) = n(1/2 . III) n(1/2 ZnSO4).
III:
n(1/2 . III) = C(1/2 . III) ∙ V(1/2 . III);
n(1/2 . III) = 0,2151 ∙ 25,00 ∙ 103 = 5,38 ∙ 103 .
ZnSO4 ZnSO4 , f.(ZnSO4) = 1/2 (. 6.2):
(1/2 ZnSO4) = (ZnSO4): 1/2 = 0,1015: 1/2 = 0,2030 /;
|
|
n(1/2 ZnSO4) = 0,2030 ∙ 9,83 ∙ 103 = 2,00 ∙ 103 .
Al3+
n(1/2 Al3+) = 5,38 ∙ 103 2,00 ∙ 103 = 3,38 103 .
f.(Al2O3) :
Al2O3 → 2 Al3+
f. (Al2O3) = (1/2)/ 2 = 1/4.
m(Al2O3) M(1/4 Al2O3) = 25,4903:
m(Al2O3) = n(1/2 Al3+) ∙ M(1/4 Al2O3) = 3,38 ∙ 103 ∙ 25,4903 = = 0,0862 ;
ω = 0,0862 / 1,0220 ∙ 100 = 8,43 %.