CBSE 2022 · Region 5 · Set 1 · Q12 · 5 marks

Read the passage given below and answer the questions that follow:

Oxidation-reduction reactions are commonly known as redox reactions. They involve transfer of electrons from one species to another. In a spontaneous reaction, energy is released which can be used to do useful work. The reaction is split into two half reactions. Two different containers are used and a wire is used to drive the electrons from one side to the other and a Voltaic/Galvanic cell is created. It is an electrochemical cell that uses spontaneous redox reactions to generate electricity. A salt bridge also connects to the half cells. The reading of the voltmeter gives the cell voltage or cell potential or electromotive force. If $\displaystyle \mathrm{E}_{\text {cell }}^{\mathrm{o}}$ is positive the reaction is spontaneous and if it is negative the reaction is non-spontaneous and is referred to as electrolytic cell. Electrolysis refers to the decomposition of a substance by an electric current. One mole of electric charge when passed through a cell will discharge half a mole of a divalent metal ion such as $\displaystyle \mathrm{Cu}^{2+}$. This was first formulated by Faraday in the form of laws of electrolysis. The conductance of material is the property of materials due to which a material allows the flow of ions through itself and thus conducts electricity. Conductivity is represented by k and it depends upon nature and concentration of electrolyte, temperature etc. A more common term molar conductivity of a solution at a given concentration is conductance of the volume of solution containing one mole of electrolyte kept between two electrodes with the unit area of cross-section and distance of unit length. Limiting molar conductivity of weak electrolytes cannot be obtained graphically.

(a)

Is silver plate the anode or cathode? $\displaystyle 1$

(b)

What will happen if the salt bridge is removed? $\displaystyle 1$

(c)

When does electrochemical cell behaves like an electrolytic cell? $\displaystyle 1$

(d)

(i)OR(d)

What will happen to the concentration of $\displaystyle \mathrm{Zn}^{2+}$ and $\displaystyle \mathrm{Ag}^{+}$when $\displaystyle \mathrm{E}_{\text {cell }}=0$.

(ii)

Why does conductivity of a solution decreases with dilution?

CBSE Class 12 Chemistry past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.