Electrochemistry - MCQ - One Answer Only

1. Faraday’s laws of electrolysis are related to the

a. atomic number of the cation.
b. atomic number of the anion.
c. equivalent weight of the electrolyte
d. speed of the cation
(JEE 1983)

Ans: ©

2. A solution containing one mole for litre each of Cu(NO3)2, AgNO3, Hg2(NO3)2 and Mg(NO3)2 is electrolysed using inert electrodes.
Standard electrode potentials in volts (reduction potentials) are:

Ag⁺| Ag = 0.80
Hg2²⁺ |Hg = 0.79
Cu²⁺|Cu = 0.34
Mg²⁺|Mg = -2.37

With increasing voltage, the sequence of deposition of metals on the cathode will be:
(JEE

a. Ag,Hg,Cu, Mg
b. Mg,Cu,Hg,Ag
c. Ag,Hg, Cu
d. Cu,Hg, Ag

Ans: ( C )


3. The electric charge or electrode deposition of one gram equivalent of a substance is:

a. one ampere for one second
b. 96,500 coulombs per second
c. one ampere for one hour
d. charge on one mole of electrons
(JEE 1984)

ans (d)

4. The reaction ½ H2(g) + AgCl(s) = H⁺(aq) + Cl^-
(aq) +Ag(s) occurs in the galvanic cell:

a. Ag|AgCl(s) |KCl(soln) |AgNO3(soln) |Ag
b.Pt|H2(g) |HCl(soln) |AgNO3(soln) |Ag
c. Pt|H2(g) |HCl(soln) |AgCl(s) |Ag
d. Pt|H2(g) |KCl(soln) |AgCl(s) |Ag
(JEE 1985)

Ans: c
In cell c reactions occurring are

AgCl(s) + e^- -> Ag(s) + Cl^-(aq)
½ H2(g) -> H⁺ (aq) + e^-

adding ½ H2(g) + AgCl(s) = H⁺(aq) + Cl^-
(aq) +Ag(s)

Electrochemistry - True or False Questions

1. The dependence of electrode potential for the electrode Mⁿ⁺ |M with conetration under STP conditions is given by the expression:

E = E° + 0.0591 V/n * log₁₀[Mⁿ⁺ |]

(JEE 1993)

False

The factor 0.0591 is applicable when the temperature is 298 K and not 273 K.

Electrochemistry - Fill Blanks Type

1. The more ___________________ the standard reduction potential, the __________________ is its ability to displace hydrogen from acids.
(JEE 1986)

Answer: negative, greater

2. The electrolysis of molten sodium hydride liberates ______________ gas at the ____________.

(JEE 1989)

Answer H2, anode

3. When an aqueous solution of sodium fluoride is electrolysed, the gas liberated at the anode is _________________ . (JEE 1997 cp)

Answer: O2