CBSE Class 12 Chemistry Electrochemistry MCQs Set A

Question : Effect of dilution on conductivity of solution:

a) Increases  
b) Decreases
c) Unchanged
d) None of the above

Answer : A

Question : Through a solution of CuSO₄ a current of 3 amperes was passed for 2 hours. At cathode 3 g of Cu²⁺ions were discharged. The current efficiency is [At. wt. of Cu = 63.5]

a) 33.3%
b) 42.2%
c) 48.7%
d) 54.4%

Answer : B

Question : Which shows electrical conductance?

a) Sodium    
b) Diamond
c) Potassium
d) Graphite

Answer : D

Question : Time required to deposit one millimole of aluminium metal by the passage of 9.65 amperes through aqueous solution of aluminium ion is

a) 30 s       
b) 10 s
c) 30,000 s
d) 10,000 s

Answer : A 

Question : The products formed when an aqueous solution of NaBr is electrolysed in a cell having inert electrodes are:

a) Na and Br₂
b) Na and O₂
c) H₂ ,Br₂ and NaOH
d) H₂ and O₂

Answer : C

Question : Equivalent conductance of an electrolyte containing NaF at infinite dilution is 90.1 Ohm^–1cm². If NaF is replaced by KF what is the value of equivalent conductance?

a) 90.1 Ohm^–1cm²
b) 111.2 Ohm^–1cm²
c) 0                        
d) 222.4 Ohm^–1cm²

Answer : A  

Question : For a cell reaction involving two electron change, the standard EMF of the cell is 0.295 V at 2°C. The equilibrium constant of the reaction at 25°C will be

a) 29.5 × 10^–2
b) 10
c) 1 × 10¹⁰    
d) 2.95 × 10^–10

Answer : C  

Question : A 0.5 M NaOH solution offers a resistance of 31.6 ohm in a conductivity cell at room temperature. What shall be the approximate molar conductance of this NaOH solution if cell constant of the cell is 0.367 cm^–1.

a) 234 S cm² mole^–1 
b) 23.2 S cm² mole^–1
c) 4645 S cm_² mole^–1
d) 5464 S cm² mole^–1

Answer : D 

Question : Which of the following statements is incorrect regarding electrochemistry?

a) It is the study of production of electricity from energy released during spontaneous chemical reactions.

b) NaOH, Cl₂, alkali and alkaline earth metals are prepared by electrochemical methods.

c) The demerit associated with electrochemical methods is that they are more polluting. Thus they are ecodestructive.

d) Electrochemical reactions are more energy efficient and less polluting.

Answer : C

Question : What flows in the internal circuit of a galvanic cell?

a) Ions

b) Electrons

c) Electricity

 d) Atoms

Answer : A

Question : Which of the following statements about galvanic cell is incorrect

a) anode is positive

b) oxidation occurs at the electrode with lower reduction potential

c) cathode is positive

d) reduction occurs at cathode

Answer : A

Question : Reaction that takes place at graphite anode in dry cell is

a) Zn²⁺ + 2e+ →Zn(s)

b) Zn(s)→Zn²⁺ + 2e-

c) Mn2+ + 2^e- →Mn(s)

d) Mn(s)→Mn- + e- +1.5V

Answer : B

Question : In which of the following conditions salt bridge is not required in a galvanic cell?

a) When galvanic cell is used in geyser.

b) When distance between oxidation half cell and reduction half cell is negligible.

c) Electrolytic solutions used in both the half cells are of same concentration.

d) When both the electrodes are dipped in the same electrolytic solution.

Answer : D

Question : Which device converts chemical energy of a spontaneous redox reaction into electrical energy?

a) Galvanic cell

b) Electrolytic cell

c) Daniell cell

d) Both a) and c)

Answer : D

Question : To deposit one equivalent weight of silver at cathode, the charge required will be

a) 9.65 × 10⁴ C

b) 9.65 × 10³ C

c) 9.65 × 10⁵ C

d) 9.65 × 10⁷ C

Answer : A

Question : The volume of oxygen gas liberated at NTP by passing a current of 9650 coulombs through acidified water is

a) 1.12 litre

b) 2.24 litre

c) 11.2 litre

d) 22.4 litre

Answer : B

Question : Three faradays electricity was passed through an aqueous solution of iron (II) bromide. The weight of iron metal (at. wt = 65) deposited at the cathode (in gm) is

a) 56

b) 84 

c) 112

d) 168

Answer : B

Question : Faraday’s laws of electrolysis will fail when

a) temperature is increased

b) inert electrodes are used

c) a mixture of electrolytes is used

d) None of these cases

Answer : D

Question : The electric charge for electrode decomposition of one gram equivalent of a substance is

a) one ampere per second

b) 96500 coulombs per second

c) one ampere for one hour

d) charge on one mole of electrons

Answer : D

Question : In electrolysis of dilute H₂SO₄ using platinum electrodes

a) H₂ is evolved at cathode

b) NH₂ is produced at anode

c) Cl₂ is obtained at cathode

d) O₂ is produced

Answer : A

Question : The difference between the electrode potentials of two electrodes when no current is drawn hrough the cell iscalled _________.

a) Cell potentials

b) Cell emf

c) Potential difference

d) Cell voltage

Answer : B

Question :  Which of the following pair(s) is/are incorrectly matched?

(i) R (resistance) – ohm (Ω)

(ii)  (resistivity) – ohm metre (Ωm)

(iii) G (conductance) – seimens or ohm (S)

(iv)  (conductivity) – seimens metre^–1 (Sm^–1)

a) (i), (ii) and (iii)

b) (ii) and (iii)

c) (i), (ii) and (iv)

d) (iii) only 

Answer : C

Question : The reference electrode is made by using

a) ZnCl₂

b) CuSO₄

c) HgCl₂

d) Hg₂Cl₂

Answer : D

Question : The standard hydrogen electrode potential is zero, because

a) hydrogen oxidized easily

b) electrode potential is considered as zero

c) hydrogen atom has only one electron

d) hydrogen is a very light element

Answer : B

Question : Without losing its concentration ZnCl₂ solution cannot be kept in contact with

a) Au

b) Al

c) Pb

d) Ag

Answer : B

Question : On the basis of the following E° values, the strongest oxidizing agent is :

[Fe(CN)₆]^4– +[Fe(CN)₆]^3– + e– ; E° = – 0.35 V

Fe2+ → Fe3+ + e–; E° = – 0.77 V

a) [Fe(CN)₆]^4–

b) Fe²⁺

c) Fe³⁺

d) [Fe(CN)₆]^3–

Answer :C

Question : Standard electrode potential of three metals X, Y and Z are – 1.2 V, + 0.5 V and – 3.0 V, espectively. The reducing powerbof these metals will be :

a) Y > Z > X

b) X > Y > Z

c) Z > X > Y

d) X > Y > Z

Answer : C

Question : Standard electrode potential for Sn⁴⁺ / Sn²⁺ couple is + 0.15 V and that for the Cr³⁺ / Cr couple is – 0.74 V. These two couples in their standard state are connected to make a cell. The cell potential will be

a) + 1.19 V

b) + 0.89 V

c) + 0.18 V

d) + 1.83 V

Answer : B

Question : Standard reduction potentials of the half reactions are given below :

F₂(g) + 2e– → 2F– (aq); E° = + 2.85 V

Cl₂(g) + 2e– → 2Cl–(aq); E° = + 1.36 V

Br₂(l) + 2e– → 2Br–(aq); E° = + 1.06 V

I₂(s) + 2e– → 2I–(aq); E° = + 0.53 V

The strongest oxidising and reducing agents respectively are

a) F₂ and I–

b) Br₂ and Cl–

c) Cl₂ and Br–

d) Cl₂ and I₂

Answer : A

Question : A button cell used in watches functions as following

Zn(s) + Ag2O(s) + H2O(l)

2Ag(s) + Zn₂+(aq) + 2OH–(aq)

If half cell potentials are :

Zn₂+(aq) + 2e– → Zn(s); Eo = – 0.76 V

Ag₂O(s) + H₂O (l) + 2e– → 2Ag(s) + 2OH–(aq); Eo = 0.34 V

The cell potential will be :

a) 0.42 V

b) 0.84 V

c) 1.34 V

d) 1.10 V

Answer : D

Question : The oxidation potentials of A and B are +2.37 and +1.66 V respectively. In chemical reactions

a) A will be replaced by B

b) A will replace B

c) A will not replace B

d) A and B will not replace each other

Answer : B

Question : A smuggler could not carry gold by depositing iron on the gold surface since

a) gold is denser

b) iron rusts

c) gold has higher reduction potential than iron

d) gold has lower reduction potential than iron

Answer : B

Question : Which cell will measure standard electrode potential of copper electrode ?

a) Pt (s) |H₂ (g, 0.1 bar) |H+ (aq., 1 M) ||Cu²⁺ (aq., 1 M) | Cu

b) Pt (s) |H₂ (g, 1 bar) |H+ (aq., 1 M) ||Cu²⁺ (aq., 2 M) | Cu

c) Pt (s) |H₂ (g, 1 bar) |H+ (aq., 1 M) ||Cu²⁺ (aq., 1 M) | Cu

d) Pt (s) |H₂ (g, 1 bar) |H+ (aq., 0.1 M) ||Cu²⁺ (aq., 1 M) | Cu

Answer : C

Question : Which of the following statement is not correct about an inert electrode in a cell ?

a) It does not participate in the cell reaction.

b) It provides surface either for oxidation or for reduction reaction.

c) It provides surface for conduction of electrons

d) It provides surface for redox reaction.

Answer : D

Question : In the electrochemical reaction 2Fe³⁺  + Zn→Zn²⁺ + 2Fe²⁺ , on increasing the concentration of Fe²⁺

a) increases cell emf

b) increases the current flow

c) decreases the cell emf

d) alters the pH of the solution

Answer : C

Question : The standard e.m.f. of a galvanic cell involving cell reaction with n = 2 is found to be 0.295 V at 25°C. The equilibrium constant of the reaction would be (Given F = 96500 C mol–1; R = 8.314JK–1mol^–1)

a) 2.0x1011

b) 4.0x1012

c) 1.0x102

d) 1.0x10¹⁰

Answer : D

Question :  On electrolysis of dilute sulphuric acid using platinum electrodes, the product obtained at the anode will be

a) hydrogen

b) oxygen

c) hydrogen sulphide

d) Sulphur dioxide

Answer : B

Question :  If 0.5 amp current is passed through acidified silver nitrate solution for 100 minutes. The mass of silver deposited oncathode, is (eq.wt.of silver nitrate = 108)

a) 2.3523 g

b) 3.3575 g

c) 5.3578 g

d) 6.3575 g

Answer : B

Question :  Molar ionic conductivities of a two-bivalent electrolytes x²⁺ and y^2- are 57 and 73 respectively. The molar conductivity of the solution formed by them will be

a) 130 S cm² mol^–1

b) 65 S cm² mol^–1

c) 260 S cm² mol^–1

d) 187 S cm² mol^–1

Answer : A

Question : The standard emf of a cell, involving one electron change is found to be 0.591 V at 25°C. The equilibrium constant of the reaction is (F = 96500 C mol^–1)

a) 1.0 × 10¹

b) 1.0 × 10⁵

c) 1.0 × 10¹⁰

d) 1.0 ×10³⁰

Answer : C

Question :  For the galvanic cell

Zn | Zn2+ (0.1M) || Cu²⁺ (1.0M)|Cu the cell potential increase if:

a) [Zn2+] is increased

b) [Cu2+] is increased

c) [Cu2+] is decreased

d) surface area of anode is increased

Answer : B

Question :  Which of the following is the use of electrolysis?

a) Electrorefining

b) Electroplating

c) Both a) & b)

d) None of these

Answer : D

Question :  An electrolytic cell contains a solution of Ag₂SO₄ and has platinum electrodes. A current is passed until 1.6 gm of O₂ has been liberated at anode. The amount of silver deposited at cathode would be

a) 107.88 gm

b) 1.6 gm

c) 0.8 gm

d) 21.60 gm

Answer : D

Question :  When 9650 coulombs of electricity is passed through a solution of copper sulphate, the amount of copper deposited is (given at. wt. of Cu = 63.6)

a) 0318g

b) 3.18 g

c) 31.8g

d) 63.6g

Answer : B

Question :  Find the charge in coulombs required to convert 0.2 mole VO3 ^–2 into VO4 –^3 –

a) 1.93 × 10⁴

b) 9.65 × 10⁴

c) 1.93 × 10⁵

d) 9.65 × 10⁵

Answer : A

Question : A silver cup is plated with silver by passing 965 coulombs of electricity. The amount of Ag deposited is :

a) 107.89 g

b) 9.89 g

c) 1.0002 g

d) 1.08 g

Answer : D

Question :  The number of coulombs required to reduce 12.3 g of nitrobenzene to aniline is :

a) 115800 C

b) 5790 C

c) 28950 C

d) 57900 C

Answer : D

Question :  The amount of electricity that can deposit 108 g of Ag from AgNO₃ solution is:

a) 1 F

b) 2 A

c) 1 C

d) 1 A

Answer : A

Question : If 0.01 M solution of an electrolyte has a resistance of 40 ohms in a cell having a cell constant of 0.4 cm^–1, then its molar conductance in ohm^–1 cm² mol^–1 is

a) 10²

b) 10⁴

c) 10

d) 10³

Answer : D

Question : Specific conductance of a 0.1 N KCl solution at 23ºC is 0.012 ohm^–1 cm^–1. Resistance of cell containing the solutionat same temperature was found to be 55 ohm. The cell constant is

a) 0.0616 cm^–1

b) 0.66 cm^–1

c) 6.60 cm^–1

d) 660 cm^–1

Answer : B

Question : The unit of equivalent conductivity is

a) ohm cm

b) ohm–1 cm² (g equivalent)–1

c) ohm cm² (g equivalent)

d) S cm^–2

Answer : B

Question : The resistance of 0.01 N solution of an electrolyte was found to be 220 ohm at 298 K using a onductivity cell with a cell constant of 0.88cm–1. The value of equivalent conductance  of solution is –

a) 400 mho cm² g eq^–1

b) 295 mho cm² g eq^–1

c) 419 mho cm² g eq–1

d) 425 mho cm2 g eq^–1

Answer : A

Question : Specific conductance of 0.1 M HNO₃ is 6.3×10^–2 ohm^–1 cm^–1. The molar conductance of the solution is

a) 100 ohm^–1 cm²

b) 515 ohm^–1 cm²

c) 630 ohm^–1 cm²

d) 6300 ohm^–1 cm² 

Answer : C

Question : The specific conductance of a 0.1 N KCl solution at 23°C is 0.012 ohm–1cm^–1. The resistance of cell containing the solution at the same temperature was found to be 55 ohm. The cell constant will be

a) 0.142 cm^–1

b) 0.66 cm^–1

c) 0.918 cm^–1

d) 1.12 cm^–1 

Answer : B

Question :  The unit of specific conductivity is

a) ohm cm^–1

b) ohm cm^–2

c) ohm^–1 cm

d) ohm^–1 cm^–1 

Answer : D

Question : Which of the following solutions of KCl will have the highest value of specific conductance?

a) 1.0 N

b) 0.1 N

c) 1.0 ×10^–2N

d) 1.0 ×10^–3N 

Answer : A

Question : The cell constant of a conductivity cell ___________.

a) changes with change of electrolyte.

b) changes with change of concentration of electrolyte.

c) changes with temperature of electrolyte.

d) remains constant for a cell.

Answer : D

Question : The standard reduction potential at 298K for the following half cells are given:
Which is the strongest reducing agent?
a) Zn(s)
b) Cr(s)
c) Both
d) None of these
Answer : A

Question : 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

Answer : C

Question : Which of the following statement is wrong about galvaniccell ?
a) cathode is positive charged
b) anode is negatively charged
c) reduction takes place at the anode
d) reduction takes place at the cathode
Answer : C

Question : In the electrolytic cell, flow of electrons if from
a) Cathode to anode in solution
b) Cathode to anode through external supply
c) Cathode to anode through internal supply
d) Anode to cathode through internal supply

Answer : C

Question : metal having negative reduction potential when dippedin the solution of its own ions, has a tendency :
a) to pass into the solution
b) to be deposited from the solution
c) to become electrically positive
d) to remain neutra
Answer : A

Question : A hydrogen electrode is immersed in a solution with pH = 0 (HCl). By how much will the potential (reduction) change if an equivalent amount of NaOH is added to the solution. (Take H₂ p = 1 atm), T = 298 K.
a) increase by 0.41 V  b) increase by 59 mV
c) decrease by 0.41 V d) decrease by 59 mV
Answer : A

Question : During the electrolysis of fused NaCl, the reaction thatoccurs at the anode is :
a) Chloride ions are oxidized
b) Chloride ions are reduced
c) Sodium ions are oxidized
d) Sodium ions are reduced
Answer : A

Question : In electroplating the article to be electroplated is made :
a) cathode
b) anode
c) either cathode or anode
d) simply suspended in the electrolytic bath.
Answer : A

Question : The electric charge for electrode deposition of one gram equivalent of a substance is
a) One ampere per second
b) 96.500 coulombs per second
c) One on one mole of electrons
d) Charge on one mole of electrons
Answer : D

Question : When a lead storage battery is discharged
a) SO₂
b) Lead is formed
c) Lead sulphate is consumed
d) Sulphuric acid is consumed
Answer : D