MHT CET202520 Apr 2025Morning ShiftChemistryElectrochemistryActual
Which from following formulae is used to obtain value of E _ cell ^* for a reaction taking place in Dry cell?
Options
- A- G^ F
- B- G^ 2 F
- C- G^ 3 F
- D- G^ 4 F
Correct answer
B. - G^ 2 F
Step-by-step solution
The standard cell potential E_ cell ^ relates to the standard Gibbs free energy change by G^ = -nFE_ cell ^ , where n is the number of electrons transferred and F is Faraday’s constant. Rearranging gives E_ cell ^ = - G^ nF . For the dry cell reaction Zn(s) + 2 MnO ₂ (s) + 2 NH ₄^+ (aq) Zn ²⁺ (aq) + Mn ₂ O ₃ (s) + 2 NH ₃ (aq) + H ₂ O(l) , oxidation yields Zn Zn ²⁺ + 2e⁻ and reduction consumes 2e⁻ per formula unit, so n = 2 . Substituting yields E_ cell ^ = - G^ 2F , corresponding to option B .