If $C + O_2 \to CO_2 + 94.2 \ kcal$,$H_2 + \frac{1}{2} O_2 \to H_2O + 68.3 \ kcal$,and $CH_4 + 2O_2 \to CO_2 + 2H_2O + 210.8 \ kcal$,then the possible heat of formation of methane will be $...... \ kcal$.

The heat of combustion of carbon monoxide at constant volume and at $17 \ ^oC$ is $-283.3 \ kJ$. Calculate its heat of combustion at constant pressure in $kJ$. $(R = 8.314 \ J \ K^{-1} \ mol^{-1})$ (in $.5$)

Hess's law of constant heat summation is based on

$C + O_2 \to CO_2; \Delta H = X$
$CO + \frac{1}{2} O_2 \to CO_2; \Delta H = Y$
Then the heat of formation of $CO$ is

When $1 \, \text{mol}$ of anhydrous salt $AB$ is dissolved in water,$21.0 \, J \, \text{mol}^{-1}$ of heat is released. The enthalpy of hydration of $AB$ is $-29.4 \, J \, \text{mol}^{-1}$. What is the enthalpy of solution of the hydrated salt $AB \cdot 2H_2O_{(s)}$ in $J \, \text{mol}^{-1}$ (in $.4$)?

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