What is the sign of the Gibbs energy change (ΔrG) of the reaction carried out in an electrolytic cell?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → ΔrG > 0
At constant temperature and pressure a reaction with ΔG < 0 is spontaneous (feasible), and one with ΔG > 0 is non-spontaneous.
An electrolytic cell uses electrical energy from an outside source to drive a non-spontaneous reaction, such as the decomposition of molten NaCl into Na and \( \ce{Cl2} \).
So the reaction it carries out has ΔrG > 0; the electrical work supplied makes up this increase in Gibbs energy.
Why the other options are incorrect
Option (2) ΔrG < 0 — Incorrect. This is the sign for a galvanic cell, where a spontaneous reaction produces electricity: ΔrG = −nFE(cell) with a positive E(cell).
Option (3) ΔrG = 0 — Incorrect. ΔrG = 0 means the reaction is at equilibrium; then E(cell) = 0 and no net reaction takes place in either direction.
NCERT (2026-27 edition):
2.1 Electrochemical Cells – “… Any further increase in the external potential again starts the reaction but in the opposite direction … It now functions as an electrolytic cell, a device for using electrical energy to carry non-spontaneous chemical reactions.”