JEE Main 2026 · 6 April · evening · Single correct · +4 / −1
For a general redox reaction
Anode Red₁→ Ox₁^(n₁⁺)+n₁e⁻
Cathode Ox₂+n₂e⁻→ Red₂^(n₂-)
Which of the following statement is incorrect?
- (a) The overall reaction can be written asn₂Red₁+n₁Ox₂⇌ n₂Ox₁^(n₁⁺)+n₁Red₂^(n₂⁻)
- (b) The electrons do not appear in the overall reaction because electrons produced at the anode are consumed at the cathode.
- (c) Here n is the number of electrons transferred in redox reaction.
- (d) If the reaction is carried out reversibly, the electrical work done is equal to the ratio of charge and potential difference through which charge is moved.
Answer and solution
Answer (d) If the reaction is carried out reversibly, the electrical work done is equal…
Solution
Chemistry ma’am · 4 steps
Electrical work is charge times potential difference, never charge divided by it. That sinks (d).
- Balance the electrons. The anode gives out n₁ electrons and the cathode takes in n₂. Multiply the anode equation by n₂ and the cathode equation by n₁, so each side handles n₁ n₂ electrons. Adding them gives the overall reaction in (a), and the electrons cancel because every electron released at the anode is used at the cathode, which is (b).
- Read the graph. The Nernst equation rearranges to (E - E°)/(RT/F) = -1/n ln Q. Against log₁₀ Q this is a straight line through the origin, and its steepness is proportional to 1/n. Here n is the number of electrons transferred in the redox reaction, so (c) is correct.
W_(elec) = q × E = nFE_(cell)
- Check the work. Moving a charge q through a potential difference E takes work q × E. In a reversible cell q = nF, so the maximum electrical work is nFE_(cell). The ratio q/E has units of C V⁻¹, which is a farad, a capacitance and not an energy.
- So. Statements (a), (b) and (c) are correct. Statement (d) is incorrect, because it calls the work a ratio when it is a product.
The idea to keep. Electrical work always means charge multiplied by potential difference, so a reversible cell gives W = nFE_(cell). Check the units: C × V = J.
Answer from the NTA final answer key. Solution by PrepWiser.