Class 12 Chemistry
Chapter 3 – Electrochemistry
Magical Series Assignment 8
Q.1. Silver is uniformly electrodeposited on a metallic vessel of surface area of 900 cm2 by passing a current of 0.5 ampere for 2 hours. Calculate the thickness of silver deposited.
Given :The density of silver is 10.5 g cm–3 and atomic mass of Ag = 108 u.
[Ans: 4.26 × 10–4 cm]
Q.2. How many coulombs are required to reduce 1 mole Cr2O72– to Cr3+?
[Ans: 5.79 × 105 C]
Q.3. How many moles of mercury will be produced by electrolysing 1.0 M Hg(NO3)2 solution with a current of 2.00 A for 3 hours?
[Ans: 0.112]
Q.4. A solution of CuSO4 is electrolysed for 10 minutes with a current of 1.5 amperes. What is the mass of copper deposited at the cathode?
[Ans: 0.296 g]
Q.5. Explain why electrolysis of aqueous solution of NaCl gives H2 at cathode and Cl2 at anode. Write overall reaction.
Given: EoNa+/Na = –2.71 V, EoH2O/H2 = –0.83 V, EoCl2/Cl– = –2.71, EoH+/H2/H2O = +1.23 V.
Q.6. (a) The cell in which the following reaction occurs:
2Fe3+(aq) + 2I–(aq) → 2Fe2+(aq) + I2(s)
has Eocell = 0.236 V at 298 K. Calculate the
standard Gibbs energy of the cell reaction.
(Given: 1 F = 96,500 C mol–1)
(b) How many electrons flow through a metallic wire if a current of 0.5 A is passed for 2 hours? (Given: 1 F = 96,500 C mol–1)
[Ans: (a) –45.548 kJ mol–1, (b) 2.25 × 1022]
Q.7. Calculate the strength of the current required to deposit 1.2 g of magnesium from molten MgCl2 in 1 hour. [1 F= 96,500 C mol–1 ; Atomic mass: Mg = 24.0 u]
[Ans: 2.68 A]
Q.8. Define Secondary batteries.
Q.9. Write the name of the cell which is generally used in hearing aids. Write the reactions taking place at the anode and the cathode of this cell.
Q.10. Write the name of the cell which is generally used in inverters. Write the reactions taking place at the anode and the cathode of this cell.
Q.11. Write the name of the cell which is generally used in transistors. Write the reactions taking place at the anode and the cathode of this cell.
Q.12. From the given cells:
Lead storage cell, Mercury cell, Fuel cell and Dry cell
Answer the following:
(i) Which cell is used in hearing aids?
(ii) Which cell was used in Apollo Space Programme?
(iii) Which cell is used in automobiles and inverters?
(iv) Which cell does not have long life?
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