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+2 ELECTRO CHEMISTRY QUESTIONS

1.         Fe²⁺ + 2e^- ® Fe(s) E^o = -0.44 volt 

            Ni²⁺ + 2e^- ®  Ni(s) E^o = -0.23 volt

The standard reduction potentials for two half reactions are given above. The Nernst equation for a galvanic cell at 25^o C in which Fe(s) reduces Ni²⁺ is the following.

E = E^o - (0.059/2)log [Fe²⁺]/[Ni²⁺]

What is the equilibrium constant for the reaction below?

Fe(s)+ Ni²⁺ ® Fe²⁺ + Ni(s)

(A) 1.9 x 10^-23

(B) 7.6 x 10^-8

(C) 3.6 x 10⁺³

(D) 1.3 x 10⁺⁷

(E) 5.2 x 10⁺²² 

2.   If a copper sample containing some zinc impurity is to be purified by electrolysis, the anode and cathode must be which of the following?

	Anode		Cathode
(A)	Pure copper		Pure zinc
(B)	Pure zinc		Pure copper
(C)	Pure copper		Impure copper sample
(D)	Impure copper sample		Pure copper
(E)	Impure copper sample		Pure zinc

3.     Zn(s) + Cu²⁺  Zn²⁺ + Cu(s)

An electrolytic cell based on the reaction above was constructed from zinc and copper half-cells. The observed voltage was found to be 1.00 volt instead of the standard cell potential, E^o, of 1.10 volts. Which of the following could correctly account for this observation?

(A) The copper electrode was larger than the zinc electrode.

(B) The Zn²⁺ electrolyte was Zn(NO₃)₂, while the Cu²⁺ electrolyte was CuSO₄.

(C) The Zn²⁺ solution was more concentrated than the Cu²⁺ solution.

(D) The solutions in the half-cells had different volumes.

(E) The salt bridge contained KCl as the electrolyte.

4.   What is the maximum mass of copper that could be plated out by electrolyzing aqueous CuCl₂ for 16.0 hours at a constant current of 3.00 amperes? (1 faraday = 96500 coulombs)

(A)   28 grams

(B)   57 grams

(C)   64 grams

(D) 114 grams


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