Bihar Board 12th Chemistry Objective Answers Chapter 3 Electrochemistry

Bihar Board 12th Chemistry Objective Questions and Answers

Electrochemistry Class 12 NCERT Solutions help to score more marks.

Bihar Board 12th Chemistry Objective Answers Chapter 3 Electrochemistry

Question 1.
Which of the following is the correct cell representation for the given cell reaction ?
Zn + H₂SO₄→ ZnSO₄ + H₂
(a) Zn|Zn²⁺||H ⁺ |H₂
(b) Zn|Zn²⁺||H ⁺ ,H₂|Pt
(c) Zn |ZnSO₄| |H₂SO₄| Zn
(d) Zn |H₂SO₄||ZnSO₄| H₂
Answer:
(b) Zn|Zn²⁺||H ⁺ ,H₂|Pt

Question 2.
The cell reaction of the galvanic cell:

(a) Hg + Cu²⁺→ Hg²⁺+Cu
(b) Hg + Cu²⁺→ Cu⁺Hg⁺
(c) Cu + Hg → CuHg
(d) Cu + Hg²⁺→ Cu²⁺ Hg
Answer:
(d) Cu + Hg²⁺→ Cu²⁺ Hg

Question 3.
Which of the following reaction is possible at anode ?
(a) 2Cr³⁺ +7H₂O → Cr₂O₇^2- + 14H⁺
(b) F₂ → 2F^–
(c) (1/2)O₂ +2H⁺ → H₂O
(d) None of these.
Answer:
(a) 2Cr³⁺ +7H₂O → Cr₂O₇^2- + 14H⁺

Question 4.
In the cell, |Zn²⁺| |Cu²⁺|Cu, the negative terminals ………..
(a) Cu
(b) Cu²⁺
(c) Zn
(d) Zn²⁺
Answer:
(c) Zn

Question 5.
In a cell reaction,

If the concentration of Cu²⁺ ions is doubled then Eº_Cell will be
(a) doubled
(b) halved
(c) increased by four times
(d) unchanged
Answer:
(d) unchanged

Question 6.
A standard hydrogen electrode that a zero potential because ……………..
(a) hydrogen can be most’easily oxidised
(b) hydrogen has only one electron
(c) the electrode potential is assumed to be zero
(d) hydrogen is the lightest element.
Answer:
(c) the electrode potential is assumed to be zero

Question 7.
Which of the following is the correct order in which metals displace each other from the salt solution of their salts  ?
(a) Zn, Al, Mg, Fe, Cu
(b) Cu, Fe, Mg, Al, Zn
(c) Mg, Al, Zn, Fe, Cu
(d) Al, Mg, Fe, Cu, Zn
Answer:
(d) Al, Mg, Fe, Cu, Zn

Question 8.
Fluorine is the best oxidising agent because it has ………..
(a) highest electron affinity
(b) highest reduction potential
(c) highest oxidation potential
(d) lowest electron affinity.
Answer:
(b) highest reduction potential

Question 9.
At 25°C, Nemst equation is …………..

Answer:
(a)

Question 10.
The correct Nernst equation for the given cell

Answer:

Question 11.
What will be the emf of the following concentration cell at 25°C ?
Ag_(s)| AgNO₃(0.01M)| | AgNO₃(0.05M)| Ag_(s)
(a) 0.828 V
(b) 0.0413 V
(c) -0.0413 V
(d) -0.828 V
Answer:
(b) 0.0413 V

Question 12.
What will be the reduction potential for the following half-cell reaction at 298 K ? [Given: [Ag⁺] = 0.1 M and
E°_e„ = +0.80 V)] ………….
(a) 0.741V
(b) 0.80 V
(c) -0.80 V
(d) -0.741V
Answer:
(a) 0.741V

Question 13.
For the cell reaction: 2Cu_(aq) → Cu_(s) + Cu²⁺ the standard ceil potential is 0.36 V. The equilibrium constant for the reaction is ………….
(a) 1.2 x 10⁶
(b) 7.4 x 10¹²
(c) 2.4 x 10⁶
(d) 5.5 x 10⁸
Answer:
(a) 1.2 x 10⁶

Question 14.
E°_cell for the reaction, 2H₂O^–+ H₃O⁺ + OH” at 25°C is -0.8277 V. The equilibrium constant for the reaction is ………….
(a) 10^-14
(b) 10^-23
(c) 10^-7
(d) 10^-21
Answer:
(a) 10^-14

Question 15.
Cell reaction is spontaneous, when …………….
(a) E°_d is negative
(b) ΔG° is negative
(c) E°_oxid is positive
(d) ΔG° is positive
Answer:
(b) ΔG° is negative

Question 16.
ΔG° f°^r the reaction, Cu²⁺+ Fe → Fe²⁺ + Cu is

(a) 11.44 kJ
(b) 180.8 kJ
(c) 150.5 kJ
(d) 28.5 kJ
Answer:
(c) 150.5 kJ

Question 17.
Units of the properties measured are given below. Which of the properties has not been matched correctly ?
(a) Molar conductance = S m² mol^-1
(b) Cell constant = m^-1
(c) Specific conductance = S m²
(d) Equivalent conductance = S m² (g eq)^-1
Answer:
(c) Specific conductance = S m²

Question 18.
Molar conductivity of 0.15 M solution of KCl at 298 K, if its conductivity is 0.0152 S cm^-1 will be
(a) 124 Ω^-1 cm²    mol^-1
(b) 204  Ω^-1 cm² mol^-1
(c) 101 Ω^-1 cm² mol^-1
(d) 300  Ω^-1 cm² mol^-1
Answer:
(c) 101 Ω^-1 cm²   mol^-1

Question 19.
The molar conductivity is maximum for the solution of concentration
(a) 0.004 M
(b) 0.002 M
(c) 0.005 M
(d) 0.001 M
Answer:
(d) 0.001 M

Question 20.
Specific conductance of 0.1 M NaCl solution is 1.01 x 10^-2 ohm^-1 cm^-1. Its molar conductance in ohm^-1 cm² mol^-1
(a) 1.01 x 10²
(b) 1.01 x 10³
(c) 1.01 x 10⁴
(d) 1.01
Answer:
(a) 1.01 x 10²

Question 21.
When water is added to an aqueous solution of an electrolyte, what is the change in specific conductivity of the electrolyte ?
(a) Conductivity decreases
(b) Conductivity increases
(c) Conductivity remain same
(d) Conductivity does not depend on number of ions
Answer:
(a) Conductivity decreases

Question 22.
Mark the correct choice of electrolytes represented in the graph.

(a) A → 4 NH₄OH, B → NaCl
(b) A →NH₄OH,B → NH₄Cl
(c) A → CH₃COOH, B → 4CH₃COONa
(d) A → KCl, B → 4 NH₄OH
Answer:
(d) A → KCl, B → 4 NH₄OH

Question 23.
Molar conductivity of NH₄OH can be calculated by the equation,

Answer:
(c)

Question 24.
Limiting molar conductivity of NaBr is
(a) Δ°_mNaBr = Δ°_mNaCl + Δ°_mKBr
(b) Δ°_mNaBr = Δ°_mNaCl + Δ°_mKBr – Δ°_mKCl
(c) Δ°_mNaBr = Δ°_mNaOH + Δ°_mNaBr – Δ°_mNaCl
(d) Δ°_mNaBr = Δ°_mNaCl – Δ°_mNaBr
Answer:
(b) Δ°_mNaBr = Δ°_mNaCl + Δ°_mKBr – Δ°_mKCl

Question 25.
Δ°_m(NH₄OH) is equal to …………..
(a) Δ°_{m (NH4OH)} + Δ°_{m (NH4a) –}  -Δ°_m(HCl)
(b) Δ°_m(NH4Cl) + Δ°_{m (NaOH) –} Δ°_m(Nao)
(c) Δ°_m(NH₄Cl) + Δ°_m(NaCl) –  Δ°_m(NaOH)
(d) Δ°_m(NaOH) +Δ°_m(NaCI) – Δ°_m(NH₄Cl)
Answer:
(b) Δ°_m(NH4Cl) + Δ°_{m (NaOH) –} Δ°_m(Naa)

Question 26.
In an electrolytic cell, the flow of electrons is
(a) from cathode to anode in the solution
(b) from cathode to anode through external supply
(c) from cathode to anode through internal supply
(d) from anode to cathode through internal supply.
Answer:
(c) from cathode to anode through internal supply

Question 27.
How long would it take to deposit 50 g of Ai from an electrolytic cell containing Al₂O₃ using a current of 105 ampere
(a) 54 h
(b) 1.42 h
(c) 32 h
(d) 2.15 h
Answer:
(b) 1.42 h

Question 28.
The charge required for reducing 1 mole of MnO₄ to Mn²⁺ is ……………….
(a) 93 x 10⁵ C
(b) 2.895 x  10⁵ C
(c) 4.28 x  10⁵ C
(d) 4.825 x  10⁵ C
Answer:
(d) 4.825 x  10⁵ C

Question 29.
How much electricity in terms of Faraday is required to  produce 100 g of Ca from molten CaCl₂ ?
(a) IF
(b) 2F
(c) 3 F
(d) 5F
Answer:
(a) IF

Question 30.
How many coulombs of electricity is required to reduce 1 mole of Cr₂O² in acidic medium ?
(a) 4 x  96500C
(b) 6 x  96500 C
(c) 2 x 96500 C
(d) 1 x  96500 C
Answer:
(b) 6 x  96500 C

Question 31.
How much metal will be deposited when a current of 12 ampere with 75% efficiency is passed through the cell for 3 h ? (Given : Z = 4 x 10^-4)
(a) 32.4 g
(b) 38.8 g
(c) 0 g
(d) 22.4 g
Answer:
(b) 38.8 g

Question 32.
How many moles of Pt may be deposited on the cathode when 0.80 F of electricity is passed through a 1.0 M solution of Pt⁴⁺ ?
(a) 0.1 mol
(b) 0.2  mol
(c) 4 mol
(d) 0.6  mol
Answer:
(b) 0.2  mol
(b) Pt⁴⁺ + 4e^– → Pt
4 moles of electricity or 4 F of electricity is required to deposit 1 mole of Pt.
0. 80 F of electricity will deposit
\(\frac{1}{4}\) 0.80 = 0.20 mol

Question 33.
If 54 g of silver is deposited during an electrolysis reaction, how much aluminium will be deposited by the same amount of electric current ?
(a) 2.7 g
(b) 4.5  g
(c) 27 g
(d) 5.4  g
Answer:
(b) 4.5g

Question 34.
During the electrolysis of dilute sulphuric acid, the following process is possible at anode.

Answer:
(a)

Question 35.
When a lead storage battery is discharged,
(a) lead sulphate is consumed
(b) oxygen gas is evolved
(c) lead sulphate is formed
(d) lead sulphide is formed.
Answer:
(c) lead sulphate is formed

Question 36.
The reaction which is taking place in nickel-cadmium battery can be represented by which of the following equation
(a) Cd + NiO₂ + 2H₂O → 4 Cd(OH)₂ + Ni(OH)₂
(b) Cd + NiO₂ + 2 OH⁺ → Ni + Cd(OH)₂
(c) Ni + Cd(OH)₂ → Cd + Ni(OH)₂
(d) Ni(OH)₂ +Cd(OH)₂ → Ni + Cd + 2H₂O
Answer:
(a) Cd + NiO₂ + 2H₂O → 4 Cd(OH)₂ + Ni(OH)₂

Question 37.
Which of the following reactions does not take place during rusting ?
(a) 4₂ CO₃ 2H⁺ + CO⁺
(b) 4Fe²⁺ + O_2(dry) → Fe₂O₃
(c) 4Fe²⁺ +O₂ +4H₂O → 2Fe₂O₃ +8H⁺
(d) Fe₂O₃ + xH₂O → Fe₂O₃. x H₂O
Answer:
(a) 4₂ CO₃ 2H⁺ + CO⁺

Question 38.
Which of the following reactions does not take place during rusting ?
(a)

(b) 4Fe²⁺ + O_2(dry) → Fe₂O₃
(c) 4Fe²⁺ + O₂ +4H₂O → 2Fe₂O₃ +8H⁺
(d) Fe₂O₃ + xH₂O → Fe₂O₃. xH₂O
Answer:
(b) 4Fe²⁺ + O_2(dry) → Fe₂O₃

Question 39.
The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called
(a) cell potential
(b) cell emf
(c) potential difference
(d) cell voltage
Answer:
(b) cell emf

Question 40.
An electrochemical cell can behave like an electrolytic cell when ___
(a) ^Ecell = 0
(b) E_{cell >} E_ext
(c) E_{extl >} E_cell
(d) E_cell = E_ext
Answer:
(c) E_{extl >} E_cell

Question 41.
Use the data given in Q. 61 and find out the most stable ion in its reduced form.
(a) Cl-
(b) Cr³⁺
(c) Cr
(d) Mn²⁺
Answer:
(d) Mn²⁺

Question 42.
Use the data of Q. 61 and find out the most stable oxidised species…….
(a) Cr³⁺
(b) MnO₄
(c) Cr₂O^2-
(d) Mn²⁺
Answer:
(a) Cr³⁺

Question 43.
The quantity of charge required to obtain one mole of aluminium from Al₂O₃ is____________
(a) 1F
(b) 6F
(c) 3F
(d) 2F
Answer:
(c) 3F

Question 44.
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) remains constant for a cell

Question 45.
While charging the lead storage battery___________
(a) PbSO₄ anode is reduced to Pb
(b) PbSO₄ cathode is reduced to Pb
(c) PbSO₄ cathode is oxidised to Pb
(d) PbSO₄ anode is oxidised to PbO₂
Answer:
(a) PbSO₄ anode is reduced to Pb