CBSE 2025 · Region 7 · Set 2 · Q27 · 3 marks
Write the name of the cell which is generally used in inverters. Write the reactions taking place at anode and cathode of this cell, when it is in use.Explain why electrolysis of an aqueous solution of NaCl gives $\displaystyle \mathrm{H}_{2}$ gas at cathode and $\displaystyle \mathrm{Cl}_{2}$ gas at anode ? Write overall reaction. \[\begin{aligned} & \text { (Given : } \mathrm{E}_{\mathrm{Na}^{+} / \mathrm{Na}}^{\circ}=-2.71 \mathrm{~V}, \mathrm{E}_{\mathrm{H}_{2} \mathrm{O} / \mathrm{H}_{2}}^{\circ}=-0.83 \mathrm{~V}, \\ & \left.\mathrm{E}_{\mathrm{Cl}_{2} / 2 \mathrm{Cl}^{-}}^{\circ}=+1.36 \mathrm{~V}, \mathrm{E}_{\mathrm{H}^{+} / \mathrm{O}_{2} / \mathrm{H}_{2} \mathrm{O}}^{\circ}=+1.23 \mathrm{~V}\right) \end{aligned} \]
Write the name of the cell which is generally used in inverters. Write the reactions taking place at anode and cathode of this cell, when it is in use.
Explain why electrolysis of an aqueous solution of NaCl gives $\displaystyle \mathrm{H}_{2}$ gas at cathode and $\displaystyle \mathrm{Cl}_{2}$ gas at anode ? Write overall reaction. \[\begin{aligned} & \text { (Given : } \mathrm{E}_{\mathrm{Na}^{+} / \mathrm{Na}}^{\circ}=-2.71 \mathrm{~V}, \mathrm{E}_{\mathrm{H}_{2} \mathrm{O} / \mathrm{H}_{2}}^{\circ}=-0.83 \mathrm{~V}, \\ & \left.\mathrm{E}_{\mathrm{Cl}_{2} / 2 \mathrm{Cl}^{-}}^{\circ}=+1.36 \mathrm{~V}, \mathrm{E}_{\mathrm{H}^{+} / \mathrm{O}_{2} / \mathrm{H}_{2} \mathrm{O}}^{\circ}=+1.23 \mathrm{~V}\right) \end{aligned} \]
Marking-scheme solution
(a)
Lead storage battery
(b)
Because at cathode the reaction with higher value of Eo is preferred and therefore, the
reduction of H2O to H2 gas is preferred
whereas at anode water should get oxidised in preference to Cl– (aq), however, on account of
overpotential of oxygen, oxidation of Cl- to Cl2 gas is preferred.
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CBSE Class 12 Chemistry past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.