Hess's law of constant heat summation includes:

What is the value of $\Delta H^{\circ}$ for the formation of ethanol from ethene gas and liquid water from the following data (in $kJ$)?
$(i)$ $C_2H_5OH_{(l)} + 3O_{2_{(g)}} \longrightarrow 2CO_{2_{(g)}} + 3H_2O_{(l)}$ $\Delta H^{\circ} = -1368 \ kJ$
$(ii)$ $C_2H_{4_{(g)}} + 3O_{2_{(g)}} \longrightarrow 2CO_{2_{(g)}} + 2H_2O_{(l)}$ $\Delta H^{\circ} = -1410 \ kJ$

If $(i)$ $C + O_2 \to CO_2$,$(ii)$ $C + 1/2 O_2 \to CO$,$(iii)$ $CO + 1/2 O_2 \to CO_2$,the heats of reaction are $Q$,$-12$,and $-10$ respectively. Then $Q =$ ?

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 $z \ kJ$?

If $C$ (diamond) $\rightarrow C$ (graphite) $+ X \ kJ \ mol^{-1}$,$C$ (diamond) $+ O_{2(g)} \rightarrow CO_{2(g)} + Y \ kJ \ mol^{-1}$,and $C$ (graphite) $+ O_{2(g)} \rightarrow CO_{2(g)} + Z \ kJ \ mol^{-1}$,at constant temperature,then which of the following relations is correct?

The heat of formation of $H_2O$ is $-286 \, kJ/mol$ and $H_2O_2$ is $-188 \, kJ/mol$. The enthalpy change for the reaction $2H_2O_2 \to 2H_2O + O_2$ is......$kJ$.