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Use delta G = delta H - T delta S to find delta G, delta H or a temperature

This type of question, asked 13 times: 3 May 2023 S1, 15 May 2023 S1, 16 May 2023 S1, 9 May 2024 S1, 14 May 2024 S2, 25 Apr 2025 S1, 25 Apr 2025 S2, 13 Apr 2026 S1, 15 Apr 2026 S2, 18 Apr 2026 S1, 12 May 2026 S1, 14 May 2026 S1, 15 May 2026 S1. All 13 questions below, oldest first.

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  1. Question 1

    3 May 2023 S1

    70
    Calculate Gibbs energy change for a reaction having ΔH=31400 J, ΔS=32 J K−1\Delta H=31400\ \text{J},\ \Delta S=32\ \text{J K}^{-1} at 1000∘C1000^\circ\text{C}.

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  2. Question 2

    15 May 2023 S1

    70
    Calculate the value of ΔG\Delta G for the following reaction. N2O4( g)⟶2NO2( g)N_{2}O_{4(\text{ }g)}\longrightarrow 2NO_{2(\text{ }g)} if ΔH=57.44 kJ\Delta H = 57.44\text{ }kJ and ΔS=176 J K−1 mol−1\Delta S = 176\text{ }J{\text{ }K}^{- 1}{\text{ }mol}^{- 1}.

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  3. Question 3

    16 May 2023 S1

    67
    The enthalpy of vaporisation of a liquid is 30 kJ mol−130\,\text{kJ mol}^{-1} and entropy of vaporisation is 75 J K−1mol−175\,\text{J K}^{-1}\text{mol}^{-1}. Calculate boiling point of liquid at 1 atm.

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  4. Question 4

    9 May 2024 S1

    67
    Calculate the value of ΔG\Delta G for following reaction at 300 K. H2O(s)⟶H2O(l)H_2O(s)\longrightarrow H_2O(l) (ΔH=7 kJ\Delta H=7\,kJ, ΔS=24.8 JK−1\Delta S=24.8\,JK^{-1})

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  5. Question 5

    14 May 2024 S2

    94
    For a reaction A + B →\rightarrow products ΔH=−84.2 kJ\Delta H = -84.2\,\text{kJ} and ΔS=−200 J K−1\Delta S = -200\,\text{J K}^{-1}. Calculate the highest value of temperature for forward spontaneity.

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  6. Question 6

    25 Apr 2025 S1

    55
    Calculate ΔH∘\Delta H^{\circ} for a reaction if ΔS∘=120JK−1\Delta S^{\circ}= 120JK^{- 1} and ΔG∘=28000 J\Delta G^{\circ}= 28000\text{ }J

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  7. Question 7

    25 Apr 2025 S2

    97
    For a certain reaction, ΔH=−210 kJ\Delta H = - 210\text{ }kJ and ΔS=−150 kJ K−1\Delta S = - 150\text{ }kJ{\text{ }K}^{- 1} Find the temperature so that ΔG=0\Delta G = 0.

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  8. Question 8

    13 Apr 2026 S1

    7
    For a certain reaction ΔH=−50\Delta H = -50 kJ and ΔS=−100\Delta S = -100 J/K find the temperature so that the reaction is spontaneous.

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  9. Question 9

    15 Apr 2026 S2

    7
    For a certain reaction, ΔH0\Delta H^0 is −345-345 kJ and ΔS0\Delta S^0 is −123 JK−1-123\ \mathrm{JK^{-1}}. At what temperature the change over from spontaneous to nonspontaneous will occur?

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  10. Question 10

    18 Apr 2026 S1

    8
    For a certain reaction, ΔH∘=40\Delta\mathrm{H}^\circ = 40 kJ and ΔS∘=80 JK−1\Delta\mathrm{S}^\circ = 80\ \mathrm{JK^{-1}}. Find the temperature so that ΔG∘=0\Delta\mathrm{G}^\circ = 0

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  11. Question 11

    12 May 2026 S1

    6
    For a certain reaction, change in enthalpy is −225-225 kJ and entropy change =−150 JK−1= -150\ \mathrm{JK^{-1}}. Find the temperature so that ΔG\Delta G is zero.

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  12. Question 12

    14 May 2026 S1

    6
    Calculate the free energy change for a certain reaction at 300300 K if ΔH\Delta H is 6060 kJ and ΔS\Delta S is −120 JK−1-120\ \mathrm{JK^{-1}}.

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  13. Question 13

    15 May 2026 S1

    5
    For the following reaction, C(s)+2H2(g)→CH4(g); ΔrH0=−75 kJ\mathrm{C}(s) + 2\mathrm{H_2}(g) \rightarrow \mathrm{CH_4}(g);\ \Delta_r H^0 = -75\ \mathrm{kJ}. Calculate ΔG0\Delta G^0 if ΔS0\Delta S^0 is 185 JK−1185\ \mathrm{JK^{-1}}.

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