CBSE Class 12 Chemistry Electrochemistry Notes and Questions

Question The weight of silver (at. wt. = 108) displaced by a quantity of electricity which displaces 5600 mL of O2 at STP will be
(a) 5.4 g
(b) 10.8 g
(c) 54.0 g
(d) 108.0 g 

Question. How many grams of cobalt metal will be deposited when a solution of cobalt(II) chloride is electrolyzed with a current of 10 amperes for 109 minutes?(1 Faraday = 96,500 C; Atomic mass of Co = 59 u)
(a) 4.0
(b) 20.0
(c) 40.0
(d) 0.66

Question. Al₂O₃ is reduced by electrolysis at low potentials and high currents. If 4.0 × 10⁴ amperes of current is passed through molten Al2O₃ for 6 hours, what mass of aluminium is produced? (Assume 100% current efficiency, at. mass of Al = 27 g mol^–1)
(a) 8.1 × 10⁴ g
(b) 2.4 × 10⁵ g
(c) 1.3 × 10⁴ g
(d) 9.0 × 10³ g 

Question. 4.5 g of aluminium (at. mass 27 amu) is deposited at cathode from Al3+ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from H+ ions in solution by the same quantity of electric charge will be
(a) 44.8 L
(b) 22.4 L
(c) 11.2 L
(d) 5.6 L 

Question. In electrolysis of NaCl when Pt electrode is taken then H2 is liberated at cathode while with Hg cathode it forms sodium amalgam. The reason for this is
(a) Hg is more inert than Pt
(b) more voltage is required to reduce H+ at Hg than at Pt
(c) Na is dissolved in Hg while it does not dissolve in Pt
(d) conc. of H+ ions is larger when Pt electrode is taken.

Question. A 5 ampere current is passed through a solution of zinc sulphate for 40 minutes. The amount of zinc deposited at the cathode is
(a) 0.4065 g
(b) 65.04 g
(c) 40.65 g
(d) 4.065 g 

Question. Sodium is made by the electrolysis of a molten mixture of about 40% NaCl and 60% CaCl2 because
(a) Ca++ can reduce NaCl to Na
(b) Ca++ can displace Na from NaCl
(c) CaCl₂ helps in conduction of electricity
(d) this mixture has a lower melting point than NaCl. 

Question. When CuSO₄ is electrolysed using platinum electrodes,
(a) copper is liberated at cathode, sulphur at anode
(b) copper is liberated at cathode, oxygen at anode
(c) sulphur is liberated at cathode, oxygen at anode
(d) oxygen is liberated at cathode, copper at anode.

Question. On electrolysis of dilute sulphuric acid using platinum electrodes, the product obtained at the anode will be
(a) hydrogen
(b) oxygen
(c) hydrogen sulphide
(d) sulphur dioxide

Question. A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as
(a) dynamo
(b) Ni-Cd cell
(c) fuel cell
(d) electrolytic cell.

Question. The efficiency of a fuel cell is given by
(a) ΔG/DS
(b) ΔG/DH
(c) ΔS/DG
(d) ΔH/DG

Question. Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because
(a) zinc is lighter than iron
(b) zinc has lower melting point than iron
(c) zinc has lower negative electrode potential than iron
(d) zinc has higher negative electrode potential than iron. 

Question. The most convenient method to protect the bottom of ship made of iron is
(a) coating it with red lead oxide
(b) white tin plating
(c) connecting it with Mg block
(d) connecting it with Pb block. 

Question. To protect iron against corrosion, the most durable metal plating on it, is
(a) copper plating
(b) zinc plating
(c) nickel plating
(d) tin plating.

Question. Effect of dilution on conductivity of solution:
(a) Increases
(b) Decreases
(c) Unchanged
(d) None of the above

Question. Through a solution of CuSO₄ a current of 3 amperes was passed for 2 hours. At cathode 3 g of Cu²⁺ions were discharged. The current efficiency is [At. wt. of Cu = 63.5] 
(a) 33.3%
(b) 42.2%
(c) 48.7%
(d) 54.4%

Question. Which shows electrical conductance? 
(a) Sodium
(b) Diamond
(c) Potassium
(d) Graphite

Question. Which cannot displace hydrogen from its compound? 
(a) Al
(b) Fe
(c) Hg
(d) Pb

Question. For reducing one mole of Cr₂O₇^2- to Cr³⁺ the charge required is :
(a) 3 × 96500 coulomb
(b) 6 ×96500 coulomb
(c) 0.3 Faradays
(d) 0.6 Faradays