The combustion enthalpies of carbon,hydrogen,and methane are $-395.5 \, kJ \, mol^{-1}$,$-285.8 \, kJ \, mol^{-1}$,and $-890.4 \, kJ \, mol^{-1}$ respectively at $25 \, ^oC$. The value of standard formation enthalpy of methane at that temperature is ..... $kJ \, mol^{-1}$.

The enthalpy of $1 \ mol$ of a compound is equal to its ...... (when it is formed from its constituent elements).

For the reaction $H_{2} + I_{2} \rightarrow 2 HI$,provide the potential energy profile diagram and prove that it is an exothermic reaction.

Given: $2Fe + \frac{3}{2} O_2 \to Fe_2O_3$,$\Delta H = -193.4 \ kJ$;
$Mg + \frac{1}{2} O_2 \to MgO$,$\Delta H = -140.2 \ kJ$.
What is the $\Delta H$ of the reaction $3Mg + Fe_2O_3 \to 3MgO + 2Fe$ in $kJ$?

"The resultant heat change in a reaction is the same whether it takes place in one or several stages." This statement is called

On the basis of the following thermochemical data: $(\Delta_fG^o H^{+}_{(aq)} = 0)$
$H_2O_{(\ell)} \rightarrow H^{+}_{(aq)} + OH^{-}_{(aq)} \,; \, \Delta H = 57.32 \, kJ$
$H_{2(g)} + \frac{1}{2} O_{2(g)} \rightarrow H_2O_{(\ell)} \,; \, \Delta H = -286.20 \, kJ$
The value of enthalpy of formation of $OH^{-}$ ion at $25 \, ^oC$ is : .............. $kJ$