CBSE Class 12 Chemistry Electrochemistry Worksheet Set C

Assignment (Electrochemistry)

1. Mention the differences between electrolytic cell and electrochemical cell.

2. what will happen when a) E_ext = 1.10 V, b) E_ext < 1.10 V and c) E_ext>1.10 V is applied on the cell Zn / Zn²⁺ || Cu²⁺/ Cu ?

3.What is SHE ? How will you determine the potential of a) Zn electrode b) Cu electrode using SHE ?

4. E⁰ Zn²⁺ / Zn = - 0.76 V and . E⁰ Cu²⁺ / Cu = + 0.34 V. What does positive and negative sign convey ?

5. Account for the following:

a) Zn displaces hydrogen from dilute HCl while Cu can not.

b) Li is the strongest reducing agent while Fluorine is strongest oxidising agent. 

c) copper sulphate solution can not be stored in zinc vessel. 

E⁰ Cu²⁺ / Cu = + 0.34 V E⁰ Zn²⁺ / Zn = - 0.76 VE⁰ Li+ / Li = - 3.05 V E⁰ F₂ /2 F- = + 2.87 V)

Question. Zn(s)+Cu²⁺(aq)→Zn²⁺(aq)+Cu(s) 
The above redox reaction is used in
a) Galvanic cell
b) Daniell cell
c) Voltaic cell
d) All of these

Answer: d

Question. The conductance of electrolytic solution kept between the electrodes of conductivity cell at unit distance but having area of cross-section large enough to accommodate sufficient volume of solution is called
a) limiting molar conductivity
b) molar conductivity
c) conductivity
d) All of the above

Answer: b

Question. For the electrochemical cell,
Ag⁻ |AgCl|KCl ||AgNO₃|Ag⁺ , the overall cell reaction is
a) Ag + KCl→ AgCl(s)+K⁺
b)  Ag + KgCl→ 2Ag+1/2Cl₂
c) AgCl(s)→ Ag⁺Cl⁻
d) Ag⁺ Cl^–  → AgCl(s)

Answer: c

Question. Calculate the standard cell potential for the following Galvanic cell, Cr|Cr³⁺||Cd |Cd²⁺ [Given, E°_Cr³⁺/C = −0.74V and  E°_Cd²⁺/Cd= −0.40V]
a) 0.74 V
b) −0.34 V
c) + 0.34 V
d) 1.14 V

Answer: c

Question. If E° Zn²⁺/Zn) −0 763 V and E° (Fe2+ /Fe) =−0.44 V, then the emf of the cell Zn|Zn²⁺ (a=0.001)||Fe²⁺    (a=0.005) | 2+ (a = )| Fe is
a) equal to 0.323 V
b) less than 0.323 V
c) greater than 0.323 V
d) equal to 1.103 V

Answer: c

Question. Electrolytic cell is a device
a) in which a non-spontaneous chemical reaction is carried out at the expense of electrical energy
b) in which a spontaneous chemical reaction is carried out to generate electrical energy
c) in which applied opposite potential is less than the cell potential
d) Both (a) and (c)

Answer: a

Question. A hydrogen gas electrode is made by dipping platinum wire in a solution of HCl at pH =10 and by passing hydrogen gas around the platinum wire at 1 atm pressure. The oxidation potential of electrode would be
a) 0.059 V
b) 0.59 V
c) 0.118 V
d) 0.18 V

Answer: b

Question. In the electrochemical cell, Zn|ZnSO₄ (0.01 M)| |CuSO₄ (1.0M) | Cu, the emf of this Daniell cell is E₁. When the concentration of ZnSO₄ is changed to 1.0 M and that of CuSO4 changed to 0.01 M, the emf changes to E₂. From the
following, which one is the correct relationship between E₁ and E₂? ( Given, RT/F= 0.059)
a) E₁ = E₂  
b) E₁ < E₂
c) E_{1 >} E₂
d) E₂ = 0 ≠ E1

Answer: c

Question. The standard Gibbs free energy of Zn (s) + Cu²+(aq)→ Zn²⁺(aq) + Cu(s) is
a) −91FE_cell
b) −2FE_cell
c) −3 FE_cell
d) −4 FE_cell

Answer: b

Question. 1.5 A current is flowing through a metallic wire. If it flows for 3 hrs, how many electrons would flow through the wire?
a) 2.05×10²² electrons
b) 1.0×10²³ electrons
c) 10²⁴ electrons
d) 4.5×10²³ electrons

Answer: b

Question. KCl solution is generally used to determine the cell constant because
a) it is highly ionic in nature
b) its conductivity is known accurately at various concentration and different temperatures
c) size of cations and anions are comparable
d) All of the above

Answer: b

Question. The resistance of the cell containing KCl solution at 23°C was found to be 55Ω. Its cell constant is 0.616 cm⁻¹. The conductivity of KCl solution (Ω⁻¹ cm⁻¹) is
a) 1.21×10⁻³
b) 1.12×10⁻²
c) 1.12×10⁻³
d) 1.21×10⁻²

Answer: b

Question. Standard electrode potential for Sn⁴⁺/ Sn²⁺ couple is +0.15V and that for the Cr³⁺/Cr  couple is −0.74V.
These two couples in their standard state are connected to make a cell. The cell potential will be
a) + 1.83 V
b) +1.19 V
c) + 0.89 V
d) + 0.18 V

Answer: c

Question. If resistance of a conductivity cell filled with 2 mol L⁻¹ KCl solution is 100 Ω. The resistance of the same cell when filled with 0.2 mol L⁻¹ KCl solution is 520 Ω. Then the conductivity of 0.2 mol L⁻¹ KCl solution will be (Given the conductivity of 1 mol L⁻¹ KCl solution is 1.29 S/m.)
a) 0.248 S cm⁻¹
b) 0.248 S m⁻¹
c) 2.48 S cm⁻¹
d) 2.48 S m⁻¹

Answer: b

Question. “Limiting molar conductivity of an electrolyte can be represented as sum of the individual contributions of anion and cation of the electrolyte”.
Which law states the above statement?
a) Henry’s law
b) Debye Onsager’s law
c) Kohlrausch’s law of independent migration of ions
d) All of the above

Answer: c

Question. Molar conductivities (Δ°_m)  at infinite dilution of NaCl, HCl and CH₃COONa  are 126.4,425.9 and 91.0 S cm² mol⁻¹ respectively. Δ°_m for CH₃ COOH will be
a) 425.5 S cm2 mol⁻¹
b) 180.5 S cm2 mol⁻¹
c) 290.85 S cm2 mol⁻¹
d) 390.5 S cm2 mol⁻¹

Answer: d

Question. A 4.0 M aqueous solution of NaCl is prepared and 500 mL of this solution is electrolysed. This leads to evolution of chlorine gas at one of the electrodes. The total charge required for the complete electrolysis will be
a) 96500 C
b) 24125 C
c) 48250 C
d) 193000 C

Answer: d

Question. When aqueous sodium chloride solution is electrolysed
a) at cathode H⁺ is reduced into H₂ instead of Na⁺
b) at cathode Na⁺ is reduced to Na
c) Cl⁻ is oxidised into Cl₂ at cathode
d) Both (b) and (c)

Answer: a

Question. Galvanisation is
a) zinc plating on aluminium sheet
b) zinc plating on iron sheet
c) iron plating on zinc sheet
d) aluminium plating on zinc sheet

Answer: b

Question. The anodic half-cell of lead-acid battery is recharged using electricity of 0.05 Faraday. The amount of PbSO₄ electrolysed in g during the process is (Molar mass of PbSO₄ =303g mol⁻¹)
a) 11.4
b) 7.6
c) 15.2
d) 22.8

Answer: b

Question. What will happen during the electrolysis of aqueous solution ofCuSO₄ in the presence of copper electrodes?
a) Copper will deposit at cathode
b) Copper will dissolve at anode
c) Oxygen will be released at anode
d) Both (a) and (b)

Answer: d

Question. A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as
a) fuel cell
b) electrolytic cell
c) dynamo
d) Ni-Cd cell

Answer: a

Please click the link below to download full pdf file for CBSE Class 12 Chemistry Worksheet - Electrochemistry.