Given the thermochemical equation,$2 H_{2(g)} + O_{2(g)} \rightarrow 2 H_2O_{(l)}$; $\Delta H = -571.6 \ kJ$. The heat of decomposition of water is:

For the reaction,$2 H_{2(g)} + O_{2(g)} \longrightarrow 2 H_{2}O_{(g)}$,$\Delta H^{\circ} = -573.2 \ kJ$. The heat of decomposition of water per mole is

State Hess's Law of Constant Heat Summation.

For which of the following reactions will the value of $\Delta H$ be positive?

Calculate $\Delta H$ in $kJ$ for the following reaction:
$C_{(s)} + O_{2(g)} \longrightarrow CO_{2(g)}$
Given that:
$H_2O_{(g)} + C_{(s)} \longrightarrow CO_{(g)} + H_{2(g)} ; \Delta H = +131 \ kJ$
$CO_{(g)} + \frac{1}{2} O_{2(g)} \longrightarrow CO_{2(g)} ; \Delta H = -282 \ kJ$
$H_{2(g)} + \frac{1}{2} O_{2(g)} \longrightarrow H_2O_{(g)} ; \Delta H = -242 \ kJ$

Calculate the heat of combustion (in $kJ$) of methane from the following data:
$(i)$ $C_{\text{(graphite)}} + 2H_{2(g)} \rightarrow CH_{4(g)} \quad \Delta H = -74.8 \ kJ$
(ii) $C_{\text{(graphite)}} + O_{2(g)} \rightarrow CO_{2(g)} \quad \Delta H = -393.5 \ kJ$
(iii) $H_{2(g)} + 1/2 O_{2(g)} \rightarrow H_2O_{(l)} \quad \Delta H = -286.2 \ kJ$