Class 12 Chemistry

Chapter 3 – Electrochemistry

Magical Series Assignment 7

 

Q.1.   (a) Write an expression for the molar conductivity of acetic acid at infinite dilution according to Kohlrausch's law.

(b) Calculate ∆^o_m for acetic acid.

Given that: ∆^o_m(HCl) = 426 S cm² mol^–1. ∆^o_m(NaCl) = 126 S cm² mol^–l.

∆^o_m(CH₃COONa) = 91 S cm² mol^–1.       [Ans: (b) 391 S cm² mol^–1]

Q.2.   Give reason: On the basis of E^o values, O₂ gas should be liberated at anode but it is Cl₂ gas which is liberated in the electrolysis of aqueous NaCl.

Q.3.   Following reactions occur at cathode during the electrolysis of aqueous silver chloride solution:

Ag⁺(aq) + e– → Ag(s) E^o = +0.80 V

H⁺(aq) + e– →  H₂(g)         E^o = 0.00 V

On the basis of their standard reduction electrode potential (E^o) values, which reaction is feasible at the cathode and why?

Q.4.   How much charge is required for the reduction of 1 mol of Zn²⁺ to Zn?

            [Ans: 193000 C]

Q.5.   Following reactions occur at cathode during the electrolysis of aqueous copper (II) chloride solution:

Cu²⁺(aq) + 2e^– → Cu(s)       E^o = +0.34 V

H⁺(aq) + e^– →  H₂(g)         E^o = 0.00 V

On the basis of their standard reduction electrode potential (E^o) values, which reaction is feasible at the cathode and why?

Q.6.   State the Faraday's first law of electrolysis.

Q.7.   Calculate the mass of Ag deposited at cathode when a current of 2 ampere was passed through a solution of AgNO₃ for 15 minutes.

(Given : Molar mass of Ag = 108 g mol^–1, 1 F = 96500 C mol^–1)

[Ans: 2.014 g]

Q.8.   How much charge in terms of Faraday is required for the reduction of 1 mol of Cu²⁺ to Cu?

[Ans: 193000 C ]

Q.9.   A solution of Ni(NO₃)₂ is electrolysed between platinum electrodes using a current of 5.0 ampere for 20 minutes. What mass of nickel will be deposited at the cathode?

(Given: At. mass of Ni = 58.7 g mol^–1, 1 F = 96500 C mol^–1)

[Ans: 1.825 g]

Q.10.   Predict the products of electrolysis in each of the following:

(i) An aqueous solution of AgNO₃ with platinum electrodes.

(ii) An aqueous solution of H₂SO₄ with platinum electrodes.

Q.11.   How much electricity in terms of Faradays is required to produce 20 g of calcium from molten CaCl₂?

[Ans: 1 F]

 

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