Verified Solution • 2025–26 Session moderate

QJEEM19Ch4180: JEE Main 2019 Chemistry - Class 12 JEEM19Ch4180 Solution: The standard electrode potential and its temperature…

The standard electrode potential Eo{E^o } and its temperature coefficient (dEodT)\left( {{{d{E^o }} \over {dT}}} \right) for a cell are 2V and −- 5 ×\times 10 −- 4 VK −- 1 at 300 K respectively.
The cell reaction is
Zn(s) + Cu2+ (aq) ⟶ Zn2+ (aq) + Cu(s)

The standard reaction enthalpy ( Δ\Delta rH o{^o } ) at 300 K in kJ mol–1 is, [Use R = 8 JK–1 mol–1 and F = 96,000C mol–1]

Multiple Choice Options

  • A −- 412.8
  • B −- 384.0
  • C 192
  • D 206.4

Step-by-Step Verified Solution

Δ\Delta G = -nFEcell = -2 ×\times 96500 ×\times 2 = -386 kJ

Δ\Delta S = nF (dEodT)\left( {{{d{E^o }} \over {dT}}} \right) = 2 ×\times 96500 ×\times ( −- 5 ×\times 10 −- 4) = -96.5 kJ

At 298 K
T Δ\Delta S = 298 ×\times (–96.5 J) = – 28.8 kJ

at constant T (=248 K) and pressure

Δ\Delta G = Δ\Delta H – T Δ\Delta S

⇒\Rightarrow Δ\Delta H = Δ\Delta G + T Δ\Delta S

= -386 - 28.8 = -412.8 kJ

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