If $C_{(s)} + O_{2(g)} \longrightarrow CO_{2(g)}; \Delta H = r$ and $CO_{(g)} + \frac{1}{2} O_{2(g)} \longrightarrow CO_{2(g)}; \Delta H = s$,then the heat of formation of $CO$ is

Which among the following represents the reaction of formation of the product?

Which of the following reactions is not exothermic?

From the following bond energies:

$H-H$ bond energy	$431.37 \text{ kJ mol}^{-1}$
$C=C$ bond energy	$606.10 \text{ kJ mol}^{-1}$
$C-C$ bond energy	$336.49 \text{ kJ mol}^{-1}$
$C-H$ bond energy	$410.50 \text{ kJ mol}^{-1}$

Enthalpy for the reaction $CH_2=CH_2 + H-H \to CH_3-CH_3$ will be .............. $\text{kJ mol}^{-1}$

Compounds with high heat of formation are less stable because

If the enthalpy of formation and enthalpy of solution of $HCl(g)$ are $-92.3 \ kJ/mol$ and $-75.14 \ kJ/mol$ respectively,then find the enthalpy of formation of $Cl^{-}(aq)$. [Assume $\Delta H_{f}(H^{+}) = 0 \ kJ/mol$]