The total enthalpy change in a chemical reaction is equal to the algebraic sum of the enthalpy changes of the individual steps of the reaction. This statement is associated with which scientist?

Compounds with high heat of formation are less stable because

The heat of neutralisation of $NH_4OH$ and $HCl$ is:

The heat of formation of $H_2O_{(l)}$ is $-68.0 \ kcal$. The heat of formation of $H_2O_{(g)}$ is likely to be........$kcal$.

Enthalpies of formation of $CCl_{4(g)}$,$H_2O_{(g)}$,$CO_{2(g)}$ and $HCl_{(g)}$ are $-105$,$-242$,$-394$ and $-92 \ kJ \ mol^{-1}$ respectively. The magnitude of enthalpy of the reaction given below is $...... \ kJ \ mol^{-1}$ (nearest integer): $CCl_{4(g)} + 2H_2O_{(g)} \rightarrow CO_{2(g)} + 4HCl_{(g)}$

The heat of combustion of methane is $-809 \, kJ \, mol^{-1}$. What is the calorific value of methane in $kJ \, g^{-1}$?