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JEE Main 202131 AugustEvening Shift
Exam
JEE Main
Year
2021
Date
31 August
Shift
Evening Shift
Subject
Chemistry
Chapter
Thermodynamics (C)

JEE Main 2021 · 31 August · Evening Shift · Chemistry · Thermodynamics (C)

The incorrect expression among the following is :

The incorrect expression among the following is :

Options

  1. AFor isothermal process wreversible=−nRTlnVfVi{w}_{\text{reversible}} = - nRTln\dfrac{{V}_{f}}{{V}_{i}}
  2. BlnK=ΔH°−TΔS°RTlnK = \dfrac{\Delta H ° - T \Delta S °}{RT}
  3. CΔGSystemΔSTotal=−T\dfrac{{\Delta G}_{\text{System}}}{{\Delta S}_{\text{Total}}} = - T (at constant P)
  4. DK=e−ΔG°/RTK = {e}^{- \Delta G ° / RT}

Correct answer

B. lnK=ΔH°−TΔS°RTlnK = \dfrac{\Delta H ° - T \Delta S °}{RT}

Step-by-step solution

ΔG=ΔG°+RTlnQ\Delta G = \Delta G ° + RTlnQ at equilibrium Q=KeqQ = {K}_{eq} and ΔG=0\Delta G = 0

ΔG°=−RTlnKeq\Delta G ° = - RT{lnK}_{eq} and ΔG°=ΔH°−TΔS°\Delta G ° = \Delta H ° - T \Delta S °

ΔH°−TΔS°=−RTlnKeq\Delta H ° - T \Delta S ° = - {RTlnK}_{eq} So, lnKeq=−(ΔH°−TΔS°)RT=(−ΔH°+TΔS°RT)lnKeq = - \dfrac{\left(\Delta H ° - T \Delta S °\right)}{RT} = \left(\dfrac{- \Delta H ° + T \Delta S °}{RT}\right)

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