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HARD TYPE
Q.1. Standard potential of following cell is 0.23V at 150C and 0.21V at 350C
Pt H2(g)|HCl(ag.)|AgCl(s)|Ag(s)
(i) Calculate n0&S0
for cell rxn . by assuming that these quantities remains unchanged in range 150& 350C.(ii) Calculate solubility of AgCl in H2O at 250C. Given, standard reduction potential of Ag+(ag.)/Ag(s) couple is 0.8v at 250C.
Ans: Pt H2
(g)|HCl(ag.)|AgCl(s)|Ag(s)
 H2  H++ e-
(Anode)
AgCl + e- Ag + Cl- (Cathode)
H2+ AgCln++ Ag + Cl- -G0= nE0
F = 1 x 0.23 x 96500 = 2219 SJ (at 250c) -G0= nE0
F = 1 x 0.21 x 96500 = 2026 SJ (at 350c)
G0=H0- TS0 - 22195 =H0- 298 xS0................................. (i)
- 20265 =n0- 308 xS0................................. (ii)
On solving S0= -96.5 J & H0= 49.987 KJ
(ii) AgAg++ e- E0OP= - 0.8 V Agcl + e- Ag + Cl-  =
AgClAg++ Cl-
 Ecell= log[AG+] ++
At eqm, Ecell= 0
 += log[Ag+][Cl-] = 0.059 logKSP AgCl
- 0.8 + 0.22 = 0.059 logKSP KSP= 1.47 x 10-10 Solubility of AgCl =
= 1.21 x 10-5mol/L
Q.2. Overall formation constant for reaction of 6 mole of CN-
with cobalt (II) is 1 x 1019. Calculate formation constant for rxn. of 6 mole of CN-with cobalt (III). Given that
CO + e- CO  = - 0.83 V CO3++ e- CO2+ = 1.82 V
Ans: CO CO + e-  = 0.83V CO3++ e- CO2+ = 1.82 V
CO
+ CO3+  CO2++ CO
Ecell= E0cell-log10
Also, 6CN-
+ CO2+ CO
& 6CN
-
+ CO3+ CO 
Ecell= E0cell+log10
At eqm. Ecell= 0 0 = 1.82 - (- 0.82) +
log10
 = 8.23 x 1044
= 8.23 x 10
63
Q.3. Show that potential areadditive for process in which half reaction are added to yeild on overall rxn. but they arenot additive when added to yeild a third half rxn.
Ans:
Case - I
: When two half rxnx. are added to give an over all rxn., no. of moles of electrons involved in each half rxn. & over all rxn. are necessarily same.
M1  + n1e - = n1 F  + n2e- M2 - = n2 F
M1+ + M2 -= n3F
 =+ n3 = n1+ n2E0 =
Since n1= n2= n3
 = + Case - II: When n1  n2 n3 M1 + n1e-
-= n1F  + (n2- h1)e- -= (n2- n1)F
M
1 + n2e-
-
= n2F
=+ n2F = n1 F + (n2- n1)F
=
Key Words
Electrolysis.
Faraday's law of electrolysis.
Transport No.
Conductance.
Specific Conductance.
Equivalent Conductance.
Molar Conductance.
Kohirausch Law.
EMF.
NErst Eq.
Cellpotential.
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E-Store
