The standard enthalpy of formation of methane, CH₄(g), is -74.8 kJ mol⁻¹. The enthalpy of atomisation of graphite, C(graphite) → C(g), is 716.7 kJ mol⁻¹, and the bond enthalpy of H₂ is 435.8 kJ mol⁻¹. What is the mean C-H bond enthalpy in methane, in kJ mol⁻¹, to the nearest integer?

ChemistryHardHigh School (11–12)Chemical Thermodynamics › Enthalpy and Hess's Law JEE Main JEE Advanced

The standard enthalpy of formation of methane, $\text{CH}_4(g)$ , is $-74.8\ \text{kJ mol}^{-1}$ . The enthalpy of atomisation of graphite, $\text{C}(\text{graphite}) \rightarrow \text{C}(g)$ , is $716.7\ \text{kJ mol}^{-1}$ , and the bond enthalpy of $\text{H}_2$ is $435.8\ \text{kJ mol}^{-1}$ . What is the mean $\text{C{-}H}$ bond enthalpy in methane, in $\text{kJ mol}^{-1}$ , to the nearest integer?

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← One mole of an ideal monatomic gas (CV = 32 R) is at 400 K and 10.0 bar in a cylinder with insulated walls. The external pressure is suddenly dropped to 2.0 bar and held there, and the gas expands against it until its own pressure is 2.0 bar. What is the final temperature of the gas?For a gas-phase reaction, Δ G° = +10.0 kJ mol⁻¹ at 300 K and Δ G° = -5.0 kJ mol⁻¹ at 400 K. Taking Δ H° and Δ S° as constant over this range, at what temperature is the equilibrium constant of the reaction equal to 1? →

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