UPSC Civil Services (Mains), Chemistry optional · 2021 · Paper I

Q4(a). E.m.f. of a hydrogen–copper cell at 25 °C

Question

Calculate the e.m.f. of the following electrochemical cell at 25 °C: Pt/H₂ (1 atm) | H⁺ (C = 0.01 M) ‖ Cu²⁺ (C = 0.1 M) | Cu (s)

Ecell = E°cell − (0.0592/2) log([H⁺]²/([Cu²⁺]pH₂)) = 0.34 + 0.0888 = 0.429 V; copper is the positive pole and ΔG = −82.7 kJ mol⁻¹.

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CoversNernst equationcell emfstandard hydrogen electrodereaction quotientGibbs energy and emf