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Enthalpy of formation of ethane from the enthalpies of combustion

The same question, asked 2 times: 14 Jun 2022*, 22 Jan 2025. Every wording below, oldest first.

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  1. Question 1

    14 Jun 2022

    124
    At 25∘C25^{\circ}C and 1 atm pressure, the enthalpies of combustion are as given below: The enthalpy of formation of ethane is

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  2. Question 2

    22 Jan 2025

    124
    Consider the following cases of standard enthalpy of reaction (ΔHr∘\left( \Delta H_{r}^{\circ} \right. in  kJmol−1)\left. \ kJmol^{- 1} \right)
    C2H6( g)+72O2( g)→2CO2( g)+3H2O(l)ΔH1∘=−1550C( graphite )+O2( g)→CO2( g)ΔH2∘=−393.5H2( g)+12O2( g)→H2O(l)ΔH3∘=−286\begin{matrix} & C_{2}H_{6}(\text{ }g) +\frac{7}{2}O_{2}(\text{ }g) \rightarrow 2CO_{2}(\text{ }g) + 3H_{2}O(l)\quad \Delta H_{1}^{\circ}= - 1550 \\ & C(\text{~graphite~}) +O_{2}(\text{ }g) \rightarrow CO_{2}(\text{ }g)\quad \Delta H_{2}^{\circ}= - 393.5 \\ & H_{2}(\text{ }g) +\frac{1}{2}O_{2}(\text{ }g) \rightarrow H_{2}O(l)\quad \Delta H_{3}^{\circ}= - 286 \end{matrix}
    The magnitude of ΔfH∘\Delta_{f}H^{\circ} of C2H6(g)C_{2}H_{6}(g) is ______\_\_\_\_\_\_ kJmol−1kJmol^{- 1} (Nearest integer).