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Electrochemistry question

2023 · 31 Jan · Shift 1 · Q12

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Electrochemistry
2023 · 31 Jan · Shift 1 · Q12

Electrochemistry question

2023 · 31 Jan · Shift 1 · Q12

JEE MainChemistryElectrochemistryMCQ+4 / −1

Which one of the following statements is correct for electrolysis of brine solution?

A
$\mathrm{O}_{2}$ is formed at cathode
B
$\mathrm{H}_{2}$ is formed at anode
C
$\mathrm{Cl}_{2}$ is formed at cathode
D
$\mathrm{OH}^{-}$ is formed at cathode

View written solutionFree

Correct answer: D

Identify the process: electrolysis of brine

Brine is an aqueous solution of sodium chloride, i.e. $\mathrm{NaCl(aq)}$ .

During electrolysis, the ions/species present are mainly:

$\mathrm{Na^+}$
$\mathrm{Cl^-}$
$\mathrm{H_2O}$

Reaction at the cathode (reduction)

At the cathode, reduction occurs. The possible reductions are:

$\mathrm{Na^+ + e^- \to Na}$
Reduction of water: $2\mathrm{H_2O} + 2e^- \to \mathrm{H_2} + 2\mathrm{OH^-}$

In aqueous solution, $\mathrm{Na^+}$ is not discharged preferentially; instead, water is reduced.

So, at the cathode: $2\mathrm{H_2O} + 2e^- \to \mathrm{H_2} + 2\mathrm{OH^-}$

Thus, $\mathrm{OH^-}$ is formed at the cathode.

Reaction at the anode (oxidation)

At the anode, oxidation occurs. In brine, chloride ions are oxidized: $2\mathrm{Cl^-} \to \mathrm{Cl_2} + 2e^-$

So, $\mathrm{Cl_2}$ is formed at the anode, not at the cathode.

Check each option

A: $\mathrm{O_2}$ is formed at cathode
False. Oxygen is not formed at cathode.
B: $\mathrm{H_2}$ is formed at anode
False. Hydrogen is formed at cathode.
C: $\mathrm{Cl_2}$ is formed at cathode
False. Chlorine is formed at anode.
D: $\mathrm{OH^-}$ is formed at cathode
True.

Conclusion

The correct statement is: $\boxed{\text{D: } \mathrm{OH^-} \text{ is formed at cathode}}$

Comparison with stored correct answer

Stored correct answer = D
Derived answer = D

They match.

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