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Standard Gibbs energy change from the enthalpy and entropy change

This type of question, asked 3 times: 2021 Paper 24, 23 Jan 2025, 5 Apr 2026 S2. All 3 questions below, oldest first.

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  1. Question 1

    2021 Paper 24

    53
    For the reaction 2NO2( g)⇌N2O4( g)2NO_{2}(\text{ }g) \rightleftharpoons N_{2}O_{4}(\text{ }g), when ΔS=−176.0JK−1\Delta S = - 176.0JK^{- 1} and ΔH=−57.8 kJ mol−1\Delta H = - 57.8\text{ }kJ{\text{ }mol}^{- 1}, the magnitude of ΔG\Delta G at 298 K298\text{ }K for the reaction is ____\_\_\_\_ kJmol−1kJmol^{- 1}. (Nearest integer)

  2. Question 2

    23 Jan 2025

    50
    The standard enthalpy and standard entropy of decomposition of N2O4N_{2}O_{4} to NO2NO_{2} are 55.0 kJ mol−155.0\text{ }kJ{\text{ }mol}^{- 1} and 175.0 J/K/mol175.0\text{ }J/K/mol respectively. The standard free energy change for this reaction at 25∘C25^{\circ}C in Jmol−1Jmol^{- 1} is ______\_\_\_\_\_\_ (Nearest integer)

  3. Question 3

    5 Apr 2026 S2

    29
    Consider the following data for the reaction X2( g)+Y2( g)⇌2XY(g)X_{2}(\text{ }g) +Y_{2}(\text{ }g) \rightleftharpoons 2XY(g) at 600 K. The ΔrG⊖\Delta_{r}G^{\ominus} (in kJ mol−1kJ\,mol^{-1}) for the reaction is:
    Compound
    ΔfH600 KΘ\Delta_{f}H_{600\text{ }K}^{\Theta}
    (kJmol−1)\left( kJmol^{- 1} \right)
    S600 KΘS_{600\text{ }K}^{\Theta}
    (Jmol−1 K−1)\left( Jmol^{- 1}{\text{ }K}^{- 1} \right)
    XY(g)XY(g)
    		42200
    X2( g)X_{2}(\text{ }g)
    		8140
    Y2( g)Y_{2}(\text{ }g)
    		80250

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