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Enthalpy of combustion of methane from enthalpies of formation

The same question, asked 2 times: 22 Apr 2025 S1*, 26 Apr 2025 S2. Every wording below, oldest first.

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  1. Question 1

    22 Apr 2025 S1

    96
    Calculate the standard enthalpy change of following reaction
    CH4( g)+2O2( g)→CO2( g)+2H2O(l)CH_{4(\text{ }g)}+ 2O_{2(\text{ }g)}\rightarrow CO_{2(\text{ }g)}+ 2H_{2}O_{(\mathcal{l})}
    If ΔfH∘(CH4)=−75 kJ mol−1\Delta_{f}H^{\circ}\left( CH_{4} \right)= - 75\text{ }kJ{\text{ }mol}^{- 1}
    ΔfH∘(CO2)=−394 kJ mol−1ΔfH∘(H2O)=−286 kJ mol−1\begin{gathered}\Delta_{f}H^{\circ}\left( CO_{2} \right)= - 394\text{ }kJ{\text{ }mol}^{- 1} \\ \Delta_{f}H^{\circ}\left( H_{2}O \right)= - 286\text{ }kJ{\text{ }mol}^{- 1}\end{gathered}

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  2. Question 2

    26 Apr 2025 S2

    75
    Calculate the standard enthalpy change of following reaction.
    CH4( g)+2O2( g)→CO2( g)+2H2O(l)CH_{4(\text{ }g)}+ 2O_{2(\text{ }g)}\rightarrow CO_{2(\text{ }g)}+ 2H_{2}O_{(\mathcal{l})}
    if ΔtH∘(CH4)=−75 kJ mol−1\Delta_{t}H^{\circ}\left( CH_{4} \right)= - 75\text{ }kJ{\text{ }mol}^{- 1}
    ΔtH∘(CO2)=−390 kJ mol−1ΔrH∘(H2O)=−286 kJ mol−1\begin{gathered}\Delta_{t}H^{\circ}\left( CO_{2} \right)= - 390\text{ }kJ{\text{ }mol}^{- 1} \\ \Delta_{r}H^{\circ}\left( H_{2}O \right)= - 286\text{ }kJ{\text{ }mol}^{- 1}\end{gathered}

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