Which of the following is not an endothermic reaction?

For which of the following reactions does the heat of reaction represent the bond energy of $HCl$?

What will be the heat of formation of methane,if the heat of combustion of carbon is $-x \ kJ$,heat of formation of water is $-y \ kJ$ and heat of combustion of methane is $z \ kJ$?

Calculate the standard enthalpy change for the following reaction: $2C_2H_6(g) + 7O_2(g) \rightarrow 4CO_2(g) + 6H_2O(l)$. Given: $\Delta_f H^{\circ}(C_2H_6) = -85 \text{ kJ mol}^{-1}$, $\Delta_f H^{\circ}(CO_2) = -390 \text{ kJ mol}^{-1}$, $\Delta_f H^{\circ}(H_2O) = -285 \text{ kJ mol}^{-1}$. (in $\text{ kJ}$)

Calculate $\Delta H$ for the reaction: $H_{2(g)} + O_{2(g)} \rightarrow H_2O_{2(g)}$ given the bond energies: $BE_{H-H} = 436 \ kJ/mol$,$BE_{O=O} = 499 \ kJ/mol$,$BE_{O-O} = 142 \ kJ/mol$,and $BE_{O-H} = 460 \ kJ/mol$. (in $kJ$)

Which of the following reactions defines the standard enthalpy of combustion,$\Delta H_c^ \circ$?