CBSE Class 12 Chemistry Electrochemistry Worksheet Set A

Question. Which one of the following metals could not be obtained on electrolysis of aqueous solution of its salts?
a. Ag
b. Mg
c. Cu
d. Cr
Answer : B

Question. On the electrolysis of aqueous solution of sodium sulphate, on cathode we get:
a. Na
b. H2
c. SO2
d. SO3
Answer : B

Question. A solution of sodium sulphate in water is electrolysed using inert electrodes. The products at the cathode and anode are respectively:
a. H₂ , O₂
b. O₂ , H₂
c. O₂ , Na
d. O₂, SO₂
Answer : A

Question. During electrolysis of NaCl solution, part of the reaction is Na⁺ + e^- → Na. This is termed as:
a. Oxidation
b. Reduction
c. Deposition
d. Cathode reaction
Answer : B

Question. Degree of ionisation of a solution depends upon:
a. Temperature
b. Nature of the electrolyte
c. Nature of the solvent
d. None of these
Answer : D

Question. Which of the following is not a non electrolyte?
a. Acetic acid
b. Glucose
c. Ethanol
d. Urea
Answer : A

Question. A certain current liberated 0.504 gm of hydrogen in 2 hours. How many grams of copper can be liberated by the same current flowing for the same time in a copper sulphate solution?
a. 12.7 gm
b. 15.9 gm
c. 31.8 gm
d. 63.5 gm
Answer : B

Question. On passing one faraday of electricity through the electrolytic cells containing Ag⁺ , N²⁺ and  Cr⁺³ ions solution, the deposited Ag (At. wt. = 108), Ni (At.wt. = 59) and Cr (At.wt. = 52) is:
        Ag                   Ni                      Cr
a. 108 gm           29.5 gm           17.3 gm
b. 108 gm           59.0 gm           52.0 gm
c. 108.0 gm        108.0 gm         108.0 gm
d. 108 gm           117.5 gm         166.0 gm
Answer : A

Question. Given 1 l / a 0.5cm ,R 50ohm,N 1.0 = − = = . The equivalent conductance of the electrolytic cell is:
a. 1 2 1 10ohm cm gmeq − −
b. 1 2 1 20ohm cm gmeq − −
c. 1 2 1 300ohm cm gmeq − −
d. 1 2 1 100ohm cm gmeq − −
Answer : A

Question. Which one is not a conductor of electricity?
a. NaCl (aqueous)
b. NaCl (solid)
c. NaCl (molten)
d. Ag metal
Answer : B

Assertion and Reason

Note: Read the Assertion (A) and Reason (R) carefully to mark the correct option out of the options given below:
a. If both assertion and reason are true and the reason is the correct explanation of the assertion.
b. If both assertion and reason are true but reason is not the correct explanation of the assertion.
c. If assertion is true but reason is false.
d. If the assertion and reason both are false.
e. If assertion is false but reason is true.

Question. Assertion: A large dry cell has high e.m.f.
Reason: The e.m.f. of a dry cell is proportional to its size.
Answer : B

Question. Assertion: The resistivity for a substance is its resistance when its one meter long and its area of cross section is one square meter.
Reason: The SI uints of resistivity are ohm metre (Ωm) and ohm centimeter (cm).
Answer : 

Question. Assertion: Ifλ^o_Na . + Λ^o_Cl- are molar limiting conductivity of the sodium and chloride ions respectively, then the limiting molar conducting for sodium chloride is given by the equation: λ^o_NaCl = λ^o_Na . + Λ^o_Cl-
Reason: This is according to Kohlrausch law of independent migration of ions.
Answer : A

Question. Assertion: For a cell reaction Zn(s) Cu²⁺ (aq) → Zn²⁺ (aq) Cu(aq); + + at the equilibrium, voltmeter gives zero reading.
Reason: At the equilibrium, there is no change in the concentration of Cu²⁺ and Zn²⁺ ions.
Answer : A

Question. Assertion: A negative value of standard reduction potential means that reduction take place on this electrode with reference to standard hydrogen electrode.
Reason: The standard electrode potential of a half cell has a fixed value.
Answer : C

Question. Assertion: Weston is a standard cell.
Reason: Its e.m.f. does not change with temperature.
Answer : A

Question. Assertion: Galvanised iron does not rust.
Reason: Zinc has a more negative electrode potential than iron.
Answer : A

Question. Assertion:  Ni / Ni²⁺ (1.0 M) || Au³⁺ (1.0M) | Au, for this cell emf is 1.75V f E^oAu³⁺ /Au = 1.50 and 
E^oNi²⁺ /Ni = 0.25 V.
Reason: Emf of the cell = E^o_cathode − E^o_anode
Answer : A

Question. Assertion: Sodium ions are discharged in preference to hydrogen ions at a mercury cathode.
Reason: The nature of the cathode can effect the order of discharge of ions.
Answer : A

Question. Assertion: In electrolysis, the quantity of electricity needed for depositing 1 mole of silver is different from that required for 1 mole of copper.
Reason: TAhe molecular weights of silver and copper are different
Answer : B

Comprehension Based

Paragraph-I

A student prepare 2 L buffer solution of 0.3 M NaH₂PO₄ and 0.3 M NaH₂PO₄ . The solution is divided in half between the two compartments (each containing 1 L buffer) of an electrolysis cell, using Pt electrodes. Assume that the only reaction is the electrolysis of water and the electrolysis is carried out for 200 min with a constant current of 0.965 A. [Assume that pKa(H₂PO^-₄) 7.2 − = ]

Question. pH at cathode is:
a. 7.2
b. 6.83
c. 7.57
d. 7.0
Answer : C

Question. pH at anode is:
a. 7.2
b. 6.83
c. 7.57
d. 7.0
Answer : B

Paragraph –II

Fuel cells: Fuel cells are galvanic cells in which the chemical energy of fuel is directly converted into electrical energy. A type of fuel cell is a hydrogen-oxygen fuel cell. It consists of two electrodes made up of two porous graphite impregnated with a catalyst (platinum, silver or metal oxide). The electrodes are placed in aqueous solution of NaOH. Oxygen and hydrogen are continuously fed into the cell. Hydrogen gets oxidized to H+ which is neutralized by OH^–, i.e., anodic reaction.
H ⇌ 2H⁺ + 2e 
2H⁺ + 2OH- ⇌ 2H₂O
H₂ + 2OH ⇌ 2H₂O + 2e⁻
At cathode, O₂ gets reduced to OH^–
Hence, the net reaction is 2H₂ + O₂ ⇌ 2H₂O
The overall reaction has ΔH = –285.6 kJ Mol^–1 and ΔG= –237.4 kJ mol^–1 at 25ºC

Question. If the cell voltage is 1.23 V for the H₂–O₂ full cell and for the half cell O₂ + 2H₂O + 4e^- ⇌ 4OH^- has E– = 0.40V then E– for 2H₂ O + 2e^- ⇌ H₂ + 2OH^- will be:
a. 0.41 V
b. 0.83 V
c. – 0.41 V
d. – 0.83 V
Answer : D

Question. What is the value of ΔS^– for the fuel cell at 25ºC?
a. 1600 J K⁻¹
b. 160 J K⁻¹
c. 160 J K⁻¹
d. 1600 J K⁻¹
Answer : B

Question. Suppose the concentration of hydroxide ion in the cell is doubled, then the cell voltage will be:
a. Reduced by half
b. Increased by a factor of 2
c. Increased by a factor of 4
d. Unchanged
Answer : D

91. A fuel cell is:
I. A voltaic cell in which continuous supply of fuels are sent at anode to perform oxidation
II. A voltaic cell in which fuels such as CH₄,H₂ and CO are used up at anode
III One which involves the reaction of H₂ — O₂ fuel cell such as:
Anode: 2H₂ 4OH^- → 4H O(I) 4e^- 
Cathode O₂ + 2H₂O(I) + 4e^- → 4OH 
IV. The efficiency of H₂ — O₂ fuel cell is 70 to 75%
a. I, III
b. I, III, IV
c. I, II, III, IV
d. I, II, III
Answer : C

Integer

Question. How many Faradays are required to reduce 1 mol of BrO₃⁻ to Br⁻ in basic medium?
Answer : 6

Question. The total number of faradays required to oxidize the following separately:
a. 1 mol of S₂O₃²⁻ in acid medium
b. 1 Equivalent of S₂O₃²⁻ in neutral medium
c. 1 mol of S₂O₃²⁻ in basic medium.
Answer : 10

Question. For the oxidation of ferric oxalate to CO₂, 18 F of electricity is required. How many moles of ferric oxalate is oxidized?
Answer : 3

Question. During the discharge of a lead storage battery, the density of 40% H₂SO₄ by weight fell from 1.225 to 0.98 (which is 20% by weight). What is the change in molarities of H₂SO₄?
Answer : 3

Question. ΔG for the reaction: 4/3Al + O₂ → 2/3Al₂O₃ is –772kJ mol^–1  of O₂. Calculate the minimum EMF in volts required to carry out an electrolysis of Al2O3.
Answer : 2

CBSE Class 12 Chemistry Electrochemistry Worksheet Set A 

           Very Short Answer

Q1)       Define electrode potential?

Q2)       Where the reduction half reaction and oxidation half reaction occurs?

Q3)       How can we connect two half-cells through a voltmeter?

Q4)       What is standard electrode potential?

Q5)       Define cell potential?

              Short Answer

Q6)       What do you understand by measurement of electrode potential?

Q7)       What is voltaic cell?

Q8)       Define electrochemistry?

Q9)       What is Gibbs free energy?

Q10)     What is Daniel cell?

              Long Answer

Q11)     Explain Nernst equation?

Q12)     State the difference between anode and cathode?

Q13)     Write short note on electrical conductance and ionic conductance?

Q14)     State the difference between electrolytic cell and galvanic cell?

Q15)     State the difference between conductivity and molar conductivity?

Please click on below link to download CBSE Class 12 Chemistry Electrochemistry Worksheet Set A