CBSE Class 12 Chemistry Electrochemistry MCQs Set C

Question: What flows in the intemal circuit of a galvanic cell?
a) Ions
b) Electrons 
c) Electricity
d) Atoms
Answer: a

Question: What will be pH of aqueous solution of electrolyte in electrolytic cell during electrolysis of CuSO₄ ( aq) between graphite electrodes? 
a) pH = 14.0
b) pH > 7.0
c) pH < 7.0
d) pH = 7.0
Answer: c

Question: 9.65 C of electric current is passed through fused anhydrous MgCI₂ . The magnesium metal thus obtained is completely converted into a Grignard reagent. The number of moles of Grignard reagent obtained is 
a) 5 x 10^-4
b) 1 x 10^-4
c) 5 X 10^-5
d) 1 X 10^-5
Answer: c

Question: In acidic medium MnO₄ is converted to Mn 2+. The quantity of electricity in Faraday required to reduce 0.5 mole of MnO₄ to Mn²⁺ would be 
a) 2.5
b) 5
c) 1
d) 0.5
Answer: a

Question: Ionisation depends upon
a) pressure
b) volume
c) dilution
d) None of the options
Answer: c

Question: A silver cup is plated with silver by passing 965 C 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 highest electrical conductivity of the following aqueous solutions is of 
a) 0.1 M difluoroacetic acid
b) 0.1 M fluoroacetic acid
c) 0.1 M chloroacetic acid
d) 0.1 M acetic acid
Answer: a

Question: By passing 9.65 A current for 16 min 40 s, the volume of O₂ liberated at STP will be 
a) 280 mL
b) 560 mL
c) 1120 mL
d) 2240 mL
Answer: c

Question: What is the quantity of electricity (in Coulombs) required to deposit all the silver from 250 mL of 1 MAgNO₃ solution ? 
a) 2412.5
b) 24125
c) 4825.0
d) 48250
Answer: b

Question: The quantity of electricity required to libreate 112 cm³ of hydrogen at STP from acidified water is 
a) 965 Coulombs
b) 1 Faraday
c) 0.1 Faraday
d) 96500 Coulombs
Answer: a

Question: Impure copper containing Fe, Au, Ag as impurities is elect:rolytically refined. A current of 140 A for 482.5s and decreased the mass of the anode by 22.26 g and increased the mass of cathode by 22.011 g percentage of iron in irnpw·e copper is (given molar mass Fe = 55.5 g / mo~ molar mass of Cu = 63 .54 g/mol) 
a) 0.95
b) 0.85
c) 0.97
d) 0.9
Answer: d

Question: During the electrolysis of molten NaCl solution, 230 g of sodium metal is deposited on the cathode, then how many moles of chlorine will be obtained at anode? 
a) 10.0
b) 5.0
c) 35.5
d) 17.0
Answer: b

Question: When during electrolysis of a solution of AgNO₃, 9650C of charge pass through the electroplating bath, the mass of silver deposited on the cathode will be 
a) 1.08 g
b) 10.8 g
c) 2 1.6 g
d) 108 g
Answer: b

Question: Molar conductance of electrolytic solution A_m is 
a) ∝ /
b) ∝(1/ A)
c) ∝ (1/C)
d) ∝ (✓C)
Answer: c

Question: Give the products available on the cathode and the anode respectively during the electrolysis of an aqueous solution of MgSO₄ between inert electrodes. 
a) H₂ (g) and O₂ (g )
b) O₂ (g) and H₂ (g)
c) O₂ (g) and Mg (s)
d) O₂ (g) and SO₂ (g)
Answer: a

Question: A solution of CuSO₄ is electrolysed for 10 min with a current of 1.5 A. What is the mass of copper deposited at the cathode? 
a) 2.096 g
b) 0.296 g
c) 3.029 g
d) 2.906 g
Answer: b

Question: 1n the electrolysis of acidulated water, it is desired to obtain 1.12 cc of hydrogen per second under STP condition. The current to be passed is 
a) 1.93 A
b) 9.65 A
c) 19.3 A
d) 0.965 A
Answer: b

Question: The amount of electricity required to produce one mole of copper from copper sulphate solution will be
a) 1 F
b) 2.33 F
c) 2 F
d) 1.33 F
Answer: c

Question: When same quantity of electricity is passed through aqueous AgNO₃ and H₂SO₄ solutions connected in series, 5.04 x 10^-2 g of H₂ is liberated. What is the mass of silver (in grams) deposited? (Eq. wts. ofhydrogen= 1. 008, silver = 108)
a) 54
b) 0.54
c) 5.4
d) 10.8
Answer: c

Question: What is the effect of dilution on the equivalent conductance of strong electrolyte ? 
a) Decreases on dilution
b) Remains unchanged
c) Increases on dilution
d) None of the options
Answer: c

Question: Suppose that gold is being plated on to another metal in an electrolytic cell. The half reaction producing the Au(s) is AuCl₄ → Au(s)+4CI^– – 3e^– Ifa 0.30 A current run for 15 min, what mass of Au(s)will be plated, assuming all the electrons are used in the reduction of AuCI₄? The Faraday constant is 96485 c/mol and molar mass of Au is 197. 
a) 0.184 g Au
b) 0.551 g Au
c) 1.84 g Au
d) 0.613 g Au
Answer: a

Question: When electric current is passed through acidified water for1930 s, 1120 mL of H₂ gas is collected (at STP) at the cathode. What is the current passed in amperes?
a) 0.05
b) 0.50
c) 5.0
d) 50 
Answer: c

Question: When 9.65 C of elecricity is passed through a solution of silver nitrate (atomic mass of Ag = l 08 g mol^-1), the amount of silver deposited is 
a) 16.2mg
b) 21.2mg
c) 10.8 mg
d) 6.4 mg
Answer: c

Question: Calculate the volume of H₂ gas at NTP obtained by passing 4 A through acidified H₂O for 30 min is 
a) 0.0836 L
b) 0.0432 L
c) 0.1672 L
d) 0.836 L
Answer: d

Question: Silver is monovalent and has an atomic mass of 108. Copper is divalent and has an atomic mass of 63.6. The san1e electric current is passed, for the same length of time through a silver coulometer and a copper coulometer. If 27 .0 g of silver is deposited, then the coorresponding amount of copper deposited is 
a) 63.60 g
b) 31.80 g
c) 15.90 g
d) 7.95 g
e) 4.00 g
Answer: d

Question: The approx.inmte time duration in hours to electroplate 30g of calcium from molten calcium chloride using a cwrent of 5 A is (At. mass of Ca = 40) 
a) 80
b) 10
c) 16
d) 8
Answer: d

Question: The amount of silver deposited on passing 2 F of electricity through aqueous solution of AgNO₃ is 
a) 54g
b) 108g
c) 216g
d) 324g
Answer: c

Question: Two different electrolytic cells filled with molten Cu(NO₃ )₂ and molten Al(NO₃ )₃ respectively are connected in series. When electricity is passed 2.7 g Al is deposited on electrode. Calculate the weight of Cu deposited on cathode. (Cu= 63.5, Al= 27.0 g mol^-1 ) 
a) 190.5 g
b) 9.525 g
c) 63.5 g
d) 31.75 g
Answer: b

Question: Given, l / a= 0. 5 cm^-1 , R = 50 ohm, N = 1.0. The equivalent conductance of the electrolytic cell is 
a) 10 Ω^-1 cm² equiv^-1
b) 20 Ω^-1 cm² equiv^-1
c) 300 Ω^-1 cm² equiv^-1
d) 100 Ω^-1 cm² equiv^-1
Answer: a

Question: Read the following statement and predict the corresponding law? ‘At infinite dilution when dissociation is complete, each ion makes a definite contribution towards total equivalent conductance of the electrolyte itrespective of the nature of the ion. 
a) Ostwald’s-dilution law
b) Kohlrausch’s law
c) Nernst equation
d) Ohm’s law
Answer: b

Question: In a hydrogen-oxygen fuel cell, combustion of hydrogen occurs to 
a) generate heat
b) create potential difference between the two electrodes
c) produce high purity water
d) remove adsorbed oxygen from electrode surfaces
Answer: b

Question: The amount of substance deposited by the passage of lA of ctment for l s is equal to 
a) equivalent mass
b) molecular mass
c) electrochemical equivalent
d) specific equivalent
Answer: c

Question: Use of electrolysis is not done in 
a) production of Na
b) production of water
c) pmification of metals
d) production of KOH
Answer: b

Question: During charging of lead storage battery, the reaction occurring at the anode is 
a) Pb²⁺ + 2e^– → Pb
b) Pb → Pb ²⁺ + 2e^–
c) PbSO₄ + 2H₂O → 2PbO₂ + 4H⁺ + SO₄^2- + 2e^–
d) Pb²⁺ + SO₄^2- → PbSO₄
Answer: c

Question: Which of the following statements (or equation) is correct ? 
a) The units ofcell emf are Y.cm^-1
b) ΔG =- nF/E_cell
c) ln galvanic cell, chemical energy is transformed into electrical energy
d) Oxidation state of Mn in potassium permanganate is + 6
Answer: c

Question: Which one of the following has the highest molar conductivity ? 
a) Diaminedichloroplatinum (II)
b) Tetraaminedichlorocobalt (III) chloride
c) Potassium hexacyanoferrate (II)
d) Hexaaquocbrornium (III) bromide
e) Pentacarbonyl iron (0) 
Answer: c

Question: A lamp draws a current of 1.0 A. Find the charge in coulomb used by the lamp in 60 s.
a) 0.6 C
b) 60 C
c) 600 C
d) 0.006 C
Answer: b

Question: Galvanic cell is a device in which 
a) chemical energy is converted into electrical energy
b) electrical energy is converted into chemical energy
c) chemical energy is seen in the form of heat
d) thermal energy from an outside source is used to dtive the cell reaction
Answer: a

Question: A current of 12 A is passed through an electrolytic cell containing aqueous NiSO₄ solution. Both Ni and H₂ gas are formed at the cathode. The c1ment efficiency is 60%. What is the mass of nickel deposited on the cathode per hour? 
a) 7.883g
b) 3.941g
c) 5.91g
d) 2 .645g
Answer: b

Question: The charge required to liberate one gram equivalent of an element is 
a) 96500 F
b) 1 F
c) 1 C
d) None of the options
Answer: b

Question: During electrolysis of water the volume of O₂ liberated is 2.24 dm³ . The volume of hydrogen liberated, under same conditions will be 
a) 2.24 dm³ 
b) 1.12 dm³ 
c) 4.48 dm³ 
d) 0.56 dm³
Answer: c

Question: The molar conductivities A°_naOAc and A°_HCl at infinite dilution in water at 25°C are 91.0 and 426.2 S cm²/mol respectively. To calculate A°_HOAc′ the additional value required is 
a) A°_H2O
b) A°_KCl
c) A°_NaOH
d) A°_NaCl
Answer: d

Question: If’F’ is Faraday and ‘N’ is Avogadro number, then charge of electron can be expressed as
a) F X N
b) F / N
c) N / F
d) F²N 
Answer: b

Question: Which substance is obtained in the solution on electrolysis of aqueous CuSO₄ solution using graphite electrodes?
a) H₂O
b) H₂SO₄ 
c) Na₂SO₄
d) Cu(OH)₂
Answer: a

Question: On passing 0.5 F of electricity through molten sodium chloride, sodium deposited at cathode will be 
a) 29.25 g
b) 11.50 g
c) 58.50 g
d) 0.00 g
Answer: b

Question: The cell reaction is spontaneous, when 
a) E°_red is negative
b) E°_red is positive
c) Δ.G° is negative
d) Δ.G° is positive
Answer: c

Question: Electrode potential of hydrogen electrode is ….. volt.
a) 0
b) + 1 
c) – 1
d) None of the options
Answer: a

Question: The relationship between Gibbs’ free energy change (ΔG) and emf e) ofa reversible electrochemical cell is given by
a) ΔG = nFE
b) ΔG = nF l E
c) ΔG = – nFE
d) ΔG = E l nF
Answer: c

Question: Dipping iron article into a strongly alkaline solution of sodium phosphate 
a) does not affect the article
b) forms Fe₂O₃ ·xH₂O on the sw·face
c) forms iron phosphate film
d) forms fetTic hydroxide
Answer: a

Question: Same amount of electric current is passed through solutions of AgNO₃ and HCI. If 1.08 g of silver is obtained in the first case, the amount of hydrogen liberated at STP in the second case is
a) 224 cm³
b) 1.008 g
c) 112 cm³
d) 22400 cm³ 
Answer: c

Question: Which one of the following condition will increase the voltage of the cell represented by the equation?
Cu(s)+ 2Ag⁺ (aq) ⇌ Cu²⁺ (aq) + 2Ag(s)
a) Increase in the dimension of Cu electrode
b) Increase in the dimension of Ag electrode
c) Increase in the concentration of Cu²⁺ ions
d) Increase in the concentration of Ag⁺ ions
Answer: d

Question: Resistance of a conductivity cell filled with a solution of an electrolyte of concentration 0.1 M is 100 Ω. The conductivity of this solution is 1.29 Sm^-1 . Resistance of the same cell when filled with 0.2 M of the same solution is 520 Ω. The molar conductivity of 0.02 M solution of the electrolyte will be 
a) 124 x 10^-4 S m² mol^-1
b) 1240 x 10^-4 S m² mol^-1
c) l.24 x 10^-4 S m² mol^-1
d)12.4 x 10^-4 S m² mol^-1
Answer: d

Question: Hydrogen gas is not liberated when the following metal is added to dil. HCI 
a) Ag
b) Zn
c) Mg
d) Sn
Answer: a

Question: Assertion a) A current of 96.5 A is passed into aqueous AgNO₃ solution for 100 s. The weight of silver deposited is 10.8 g (Atomic weight of Ag = 108) Reason (R) The mass of a substance deposited during the electrolysis of an electrolyte is inversely proportional to the quantity of electricity passing through the electrolyte. 
a) Both A and R are cotTect and R is the correct explanation of A
b) Both A and R are correct but R is not the correct explanation of A
c) A is cotTect but R is incorrect
d) A is incotTect but Reason is correct
Answer: c

Question: The cell, Zn l Zn²⁺ (1 M) ll Cu²⁺ (1 M) l Cu
(E°_cell = 1.10 V), was allowed to be completely dischaued at 298 K. The relative concentration of Zn²⁺ to
Cu²⁺ {[Zn^2- ] / [Cu²⁺]} is
a) antilog (24.08)
b) antilog (37.3)
c) 10^37.3
d) 9.65x 10⁴
Answer: b

Question: Given standard electrode potentials
Fe²⁺ + 2e^–→ Fe E° = – 0.440 V
Fe³⁺ + 3e^–→ Fe E° = – 0.036 V
the standard electrode potential (E°) for
Fe³⁺ + e^–→ Fe²⁺ is
a) + 0.772 V
c) +0.417V
b) – 0.772 V
d) – 0.414 V
Answer: a

Question: The standard E°_red values of A,B and C are + 0.68 V, – 2.54 V, – 0.50 V respectively. The order of their reducing power is 
a) A > B > C
b) A > C > B
c) C > B > A
d) B > C > A
Answer: d

Question: What is the time (in sec) required for depositing all the silver present in 125 mL of 1 M AgNO₃ solution by passing a current of 241.25 A ? (IF = 96500 C)
a) 10
b) 50
c) 1000
d) 100
Answer: b

Question: Electrolysis of dilute aqueous NaCl solution was canied out by passing 10 mA current. The time required to liberate 0.01 mole ofH2 gas at the cathode is (IF= 96500 C mol^-1) 
a) 9.65 x 10⁴ s
b) 19.3 x 10⁴ s 
c) 28.95 x 10⁴ s
d) 38.6 x 10⁴ s
Answer: b

Question: Aluminium oxide may be electrolysed at 1000°C to furnish aluminium metal (atomic mass= 27 u; IF= 96500C). The cathode reaction is 
 Al³⁺ + 3e^– → AI°
 To prepare 5.12 kg of aluminium metal by this method would require 
a) 5.49 x 10¹ C of electricity
b) 5.49 x 10⁴ C of electricity
c) 1.83 x 10⁷ Cofelectricity
d) 5.49 x 10⁷ C of electricity
Answer: d

Question: The laws of electrolysis were proposed by 
a) Kohlrausch
b) Faraday
c) Haber
d) Bergius
Answer: b

Question: When a quantity of electricity is passed through CuSO₄ solution, 0.16 g of copper gets deposited. If the same quantity of electricity is passed through acidulated water, then the volume of H₂ liberated at STP will be (given, atomic weight of Cu = 64) 
a) 4.0 cm³
b) 56 cm³
c) 604 cm³
d) 8.0 cm³
Answer: b

Question: The cell reaction of the galvanic cell Cu(s) l Cu²⁺ (aq) ll Hg²⁺ (aq) l Hg(/) is 
a) Hg + Cu²⁺→ Hg²⁺ + Cu
b) Hg + Cu²⁺→ Cu⁺ + Hg⁺
c) Cu + Hg → CuHg
d) Cu + Hg²⁺→ Cu²⁺ + Hg
Answer: d

Question: How long (in hours) must a current of 5.0 A be maintained to electroplate 60 g of calcium from molten CaCl₂?
a) 27 h
b) 8.3 h
c) 11 h
d) 16 h
Answer: d

Question: The cathodic reaction of a dty cell is represented by
2MnO₂ (s) + Zn²⁺ +2e^– → ZnMn₂O₄ (s)
If, there are 8 g of MnO₂ in the cathodic compartment then the time for which the dty cell will continue to give a Cllffent of 2 mA is 
a) 25.675 day
c) 12.8 day
b) 51.35 day
d) 6.423 day
Answer: b

Question: In the electrolysis of water, 1 F of electrical energy would evolve
a) l mole ofoxygen
b) 1 g atom ofoxygen
c) 8 g of oxygen
d) 22.4 L of oxygen
Answer: c

Question: Which of the following is not correct ? 
a) Aqueous solution of NaCl is an electrolyte
b) The units of electrochemical equivalent are g-coulomb
c) In the Nernst equation, n represents the number of electrons transferred in the electrode reaction
d) Standard reduction potential of hydrogen electrode is zero volt.
Answer: b

Question: The charge required for reduction of lmole of Cr₂O₇^2- ions to Cr³⁺ is 
a) 96500 C
b) 2 x 96500 C
c) 3 x 96500 C
d) 6 x 96500 C
Answer: d

Question: When electric current is passed through an ionic hydride in molten state 
a) hydrogen is liberated at anode
b) hydrogen is liberated at cathode
c) no change takes place
d) hydride ion migrates towards cathode
e) hydride ion remains in solution
Answer: a

Question: A galvanic cell is constructed using the redox reaction,
1/2 H₂ (g) + AgCl(s) = H⁺ (aq) + CI_– (aq )+ Ag(s)
it is represented as
a) Pt l H₂ (g) l HCl solution l AgNO₃ solution l Ag
b) Ag l AgCl(s) l KCl solution ll HCl solution, H₂ (g) l Pt
c) Pt l H₂ (g) l KCl solution ll AgCl(s) l Ag
d) Pt l H₂ (g ), HCl solution ll AgCl(s) l Ag
Answer: d

_{Question: The standard reduction potentials at 298 K for the following half-cell reactions are given
Zn²⁺ (aq) + 2e^– ⇌ Zn(s);-0.762 V
Cr³⁺ (aq) + 3e^– ⇌ Cr(s);- 0. 74 V
2H⁺ (aq) + 2e^– ⇌ H2 (g ); +0.00 V
Fe³⁺ (aq) + e^– ⇌ Fe²⁺ (aq); + 0.77 V
Which one of the following is the strongest reducing agent? 
a) Zn(s)
b) Cr(s)
c) H2 (s)
d) Fe²⁺(aq)}
Answer: a

Question: Zn²⁺→ Zn(s); E° = – 0.76 V
Cu²⁺→ Cu(s); E° = – 0.34 V
Which of the following is spontaneous?
a) Zn²⁺ + Cu → Zn + Cu²⁺
b) Cu²⁺ + Zn → Cu + Zn²⁺
c) Zn²⁺ + Cu²⁺→ Zn + Cu
d) None of the above
Answer: b

Question: Given, E°_{Cr³⁺/Cr³⁺} = 0.72 V, E°_{Fe²⁺/Fe⁺²} = 0.42 V
The potential for the cell
Cr/ Cr³⁺ (0.1 M) l Fe²⁺(0.0l M) I Fe is
a) 0.26 V
b) 0.399 V
c) – 0.339 V
d) – 0.26 V
Answer: a