( 21 60)
-, . , , . - .
2.2.1. K2Cr2O7 NaNO2, .
-, , , . , ().
+1 +6 -2 +1 +3 2 +1 +6 2 +3 +6 2 +1 +5 -2
K2 Cr 2O7+Na N O2+H2SO4Þ Cr 2(SO4)3+Na N O3+×××
- . , - , .. , .
2K++ Cr2O72 -+Na++ NO2 -+2H++SO42-Þ 2Cr3+ +3SO42-+Na++ NO3 -+×××
- (, , ), , (). - , , ( ).
- . , , - + 2 + ( 14 + 7 ). - ( 7 2). - 1 2 . + ( 2 +).
, , - , . - +12 (-2+14(+1)=+12), +6 (2(+3)+7×0=+6). 6. - 2 , .. 1 (-1+0=-1), +1 (-1+2(+1)=+1).
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1 Cr2O72-+14H++6e=2Cr3++7H2O | - - (Cr2O72-+14H+). |
3 NO2-+H2O=NO3-+2H++2 | - - (NO2-+H2O ). |
Cr2O72-+14H++3NO2-+3H2O=2Cr3++7H2O+3NO3-+6H+ - - -. |
, - - - : 2 +. , - : Cr2O72-+8H++3NO2-=2Cr3++4H2O+3NO3-.
- . - . - 42. : 2Cr2O7+3NaNO2+4H2SO4ÞCr2(SO4)3+3NaNO3+42+×××
, , - . K+, Na+, SO42-. , + SO42-. K2SO4. , : 2Cr2O7+3NaNO2+4H2SO4=Cr2(SO4)3+3NaNO3+42+K2SO4.
- . - , .
, , , +. 1 2 ; - 2-
2.2.2. - Mn2O3ÞMn2+ , .
3- , 6 +, 3 2. - :
: Mn2O3+6++2=2Mn2++32;
: Mn2O3+32=2Mn2++6-.
, : (Mn2O3+6+), (Mn2O3+32).
- 1 2 . 2 +. , - 2 - . 2.
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2.2.3. - Mn2+Þ Mn2O3 , .
3- - 3 2. 6 +. - 6 -, 3 2. - 3- :
:2Mn2++32= Mn2O3 +6++2 (2Mn2++32);
: 2Mn2++6-= Mn2O3 +32+2 (2Mn2++6-).
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. .
, , , . - Men+ : Men+/Me.
. ; . , KCl -.
. , , .. ; . -, +.
, . :
E(Men+/Me) = Eo(Men+/Me)+(0,059/n)lg C(Men+) (3.1)
C(Men+) , n , Eo(Men+/Me) , E(Men+/Me) C(Men+).
, ; , . , MeIn+/MeI MeIIn+/MeII, MeIn+/MeI - (), MeIIn+/MeII (), :
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|¯¯¯¯¯¯¯¯ ne ¯¯¯¯¯¯¯¯↓
- MeI/MeIn+//MeIIn+/MeII+ (3.2)
↑______|
(). - - :
= (3.3)
, (3.2), : = (MeIIn+/MeII) - (MeIn+/MeI).
3.1. , , 0,01 Co(NO3)2. .
, , . . , , , .
- : 2+/.
(3.1) .
(2+/)=(2+/)+(0,059/n)lgC(2+)=-0,28+(0,059/2)lg0,01=-0,28-0,059=-0,339.
, , Zn2+/Zn, : (Zn2+/Zn)=-0,76. (3.2) .
|¯¯¯¯ 2e ¯¯¯¯¯¯¯↓
- Zn/Zn2+// 2+/ +
↑_____|
, , .
Zn=Zn2++2 .
2++2= .
Zn + 2+= Zn2++ .
(3.3) .
= = (2+/) - (Zn2+/Zn)=-0,339-(-0,76)=0,421.
.
= (2+/) - (Zn2+/Zn)=-0,28-(-0,76)=0,48.
2+/ , Cu2+/Cu, : (Cu2+/Cu)=0,34. .
|¯¯¯¯ 2e ¯¯¯¯¯¯¯↓
- /2+// Cu2+/Cu +
↑_____|
, .
=2++2 .
Cu2++2e=Cu .
+Cu2+=Co2++Cu - .
(3.3) .
= = (Cu2+/Cu) - (2+/)=0,34 (-0,339)=0,679.
, , .
=(Cu2+/Cu) - (2+/)=0,34 (-0,28)=0,62.
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( 81 100)
, . , , , , . , .
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, . , - :
22=4++2+4 ;
22+2=2-+2 .
, , : ((4++2)/22)=1,23
(22/(2-+2))= -0,83 .
, .. ; , .. . [1]
4.1. Cd(NO3)2.
: Cd(NO3)2=Cd2++2NO3-. Cd2+ , NO3- - . , .. - (. 1). Cd2+, . ((Cd2+/Cd =-0,4B; (22/(2-+2))= -0,83), , Cd2+, . , , .
2 Cd2++2=Cd - . |
1 22=4++2+4 - . |
2Cd2++22=2Cd+4++2- . |
4.2. Rb2SO4.
Rb2SO4 : Rb2SO4=2Rb++SO42-. Rb+ , SO42- . Rb+ , SO42- . .
: (Rb+/Rb)=-2,93; (22/(2-+2))= -0,83. , .
: (S2O82-/2SO42-)=2,01; ((4++2)/22)=1,23. .
, .
2 22+2=2-+2 - . |
1 22=4++2+4 - . |
62=4-+22+4++2 - . |
, .. , m :
m=(mIt)/F (4.1)
I , t - , F=96487 , m , - n: m =/n.
:
V=(VIt)/F (4.2)
V , V , (22,4) n: V=22,4/n.
4.3. , 20 . Rb2SO4 3.
, , ( 4.2), , . , , 1 2 , 1 2 . , .
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m(2)= (2)/2=2/2=1.;V(2)=22,4/2=11,2. , .
M(2)= (2)/4=32/4=8.;V(2)=22,4/4=5,6. , .
(4.1) .
m(2)=(m(2)It)/F=(1×3×1200)/96487=0,037. .
m(2)=(m(2)It)/F=(8×3×1200)/96487=0,298. .
(4.2) .
V(2)=(V(2)It)/F=(11,2×3×1200)/96487=0,418. .
V(2)=(V(2)It)/F=(5,6×3×1200)/96487=0,209. .
.