1
IIT-JEE 1994
Subjective
+4
-0
The Edison storage cells is represented as
Fe(s) | FeO(s) | KOH (aq) | Ni2O3(s) | Ni(s)
The half-cell reactions are:
Ni2O3 + H2O (l) + 2e- $$\leftrightharpoons$$ 2NiO(s) + 2OH-; Eo = +0.40V
FeO(s) + H2O(l) + 2e- $$\leftrightharpoons$$ Fe(s) + 2OH-; Eo = -0.87V
(i) What is the cell reaction?
(ii) What is the cell e.m.f? How does it depend on the concentration of KOH?
(iii) What is the maximum amount of electrical energy that can be obtained from one mole of Ni2O3?
2
IIT-JEE 1993
Subjective
+2
-0
The standard reduction potential for the half-cell
$$NO_3^-$$ + 2H+ (aq) + e $$\to$$ NO2 (g) + H2O is 0.78 V
(i) Calculate the reduction potential in 8 M H+
(ii) What will be the reduction potential of the half-cell in a neutral solution? Assume all the other species to be at unit concentration.
3
IIT-JEE 1993
Subjective
+2
-0
Chromium metal can be plated out from an acidic solution containing CrO3 according to the following equation
CrO3 (aq) + 6H+ (aq) + 6e- $$\to$$ Cr(s) + 3H2O
Calculate (i) how many grams of chromium will be plated out by 24,000 coulombs and (ii) how long will it take to plate out 1.5 g of chromium by using 12.5 amp current.
4
IIT-JEE 1992
Subjective
+4
-0
For the galvanic cell
Ag | AgCl(s), KCl (0.2M) || KBr (0.001M), AgBr(s) | Ag
Calculate the EMF generated and assign correct polarity to each electrode for a spontaneous process after taking into account the cell reaction at 25oC.
[Ksp(AgCl) = 2.8 $$times$$ 10-10; Ksp(AgBr) = 3.3 $$times$$ 10-13]
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