MCQs On Cell Constant and Electrochemical Cells

Simple electrochemical cells have characteristic time constants associated with them. The cell time constant may be thought of as the time it takes for the electrical double layer at a polarizable working electrode to be charged or discharged. A simple cell can be viewed as a series combination of solution resistance and a double-layer capacitance, and the time constant for such a combination is simply the sum of resistance and capacitance. A device that transforms chemical energy into electrical energy is called an electrochemical cell, or a galvanic cell, or a voltaic cell. In an electrochemical cell, a spontaneous redox reaction is conducted indirectly, and during the spontaneous chemical process which appears as electrical energy decreases in free energy.

1. Oxygen has +2 oxidation state in

  1. H2O
  2. H2O2
  3. F2O
  4. SO2

Answer: (c)

2. Which of the following is the strongest reducing agent?

  1. Li
  2. Na
  3. Mg
  4. Ca

Answer: (a)

3. When the salt bridge is removed from a cell, its voltage

  1. will increase
  2. will decrease to half
  3. will decrease to zero
  4. will not change

Answer: (c)

4. When a dilute solution of H2SO4 is electrolysed using platinum electrode at atode the gas evolved is

  1. SO3
  2. SO2
  3. H2
  4. O2

Answer: (d)

5. Oxidation number of sulphur in caro’s acid is

  1. +4
  2. +5
  3. +6
  4. +8

Answer: (c)

6. Which of the following is the most powerful reducing agent?

  1. H2S
  2. H2SO3
  3. SnCl2
  4. HNO2

Answer: (c)

7. Which of the following substances can act as both oxidising and reducing agent?

  1. KMnO4
  2. K2Cr2O7
  3. HNO3
  4. H2O2

Answer: (d)

8. Electrolytes conduct electric current

  1. by the movement of ions
  2. by the movement of atoms
  3. by the movement of molecules
  4. by the movement of electrons from cathode to anode

Answer: (d)

9. Reductant may be defined as a substance the oxidation no of whose atom

  1. increases
  2. decreases
  3. remains constant
  4. may increases or decreases

Answer: (a)

10. Which of the following is not an example of an oxidizing agent?

  1. hydrogen peroxide
  2. potassium dichromate
  3. nitric acid
  4. hydrogen sulphide

Answer: (d)

11. The conductance in electrolyte conductors is due to

  1. Either movement of electrons or ions
  2. Flow of free mobile electrons
  3. Movement of ions
  4. None of the above

Answer: (c)

12. The cell constant of a conductivity cell

  1. Changes with change of concentration of electrolyte
  2. Remains constant for a cell
  3. changes with change of electrolyte
  4. changes with change in temperature

Answer: (b)

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