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Electrochemistry question

2005 · Shift 0 · Q33
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Electrochemistry question

2005 · Shift 0 · Q33

JEE MainChemistryElectrochemistryMCQ+4 / −1
For a spontaneous reaction the ∆G , equilibrium constant (K) and EcelloE_{cell}^oEcello​ will be respectively
  1. A
    -ve, >1, +ve
  2. B
    +ve, >1, -ve
  3. C
    -ve, <1, -ve
  4. D
    -ve, >1, -ve
View written solutionFree

Correct answer: A

  1. For a spontaneous reaction, the Gibbs free energy change must be negative: ΔG<0\Delta G < 0ΔG<0

  2. The relation between standard free energy change and equilibrium constant is: ΔGo=−RTln⁡K\Delta G^o = -RT \ln KΔGo=−RTlnK For spontaneity under standard conditions, ΔGo<0\Delta G^o < 0ΔGo<0, so: −RTln⁡K<0-RT\ln K < 0−RTlnK<0 Since RT>0RT>0RT>0, this implies: ln⁡K>0⇒K>1\ln K > 0 \Rightarrow K>1lnK>0⇒K>1

  3. The relation between free energy and cell potential is: ΔGo=−nFEcello\Delta G^o = -nF E_{\text{cell}}^oΔGo=−nFEcello​ For a spontaneous cell reaction, ΔGo<0\Delta G^o<0ΔGo<0, hence: −nFEcello<0-nF E_{\text{cell}}^o < 0−nFEcello​<0 Since nF>0nF>0nF>0, we get: Ecello>0E_{\text{cell}}^o > 0Ecello​>0

  4. Therefore, for a spontaneous reaction:

    • ΔG\Delta GΔG is negative
    • K>1K>1K>1
    • EcelloE_{\text{cell}}^oEcello​ is positive
  5. Checking options:

    • A: −ve,>1,+ve-\text{ve}, >1, +\text{ve}−ve,>1,+ve ✅
    • B: +ve,>1,−ve+\text{ve}, >1, -\text{ve}+ve,>1,−ve ❌
    • C: −ve,<1,−ve-\text{ve}, <1, -\text{ve}−ve,<1,−ve ❌
    • D: −ve,>1,−ve-\text{ve}, >1, -\text{ve}−ve,>1,−ve ❌

Hence, the correct option is A.

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