According to Hess's Law,the enthalpy change of a reaction depends on which of the following?

The heat of combustion of ethanol into carbon dioxide and water is $-327 \ kcal$ at constant pressure. The heat evolved (in $cal$) at constant volume and $27^{\circ} C$ (assuming all gases behave ideally) is $\left( R = 2 \ cal \ mol^{-1} \ K^{-1} \right)$

Calculate the enthalpy change of vaporisation of benzene if $13 \ g$ of benzene vaporised by supplying $5.1 \ kJ$ of heat.

The heats of combustion of rhombic and monoclinic sulphur are respectively $70960 \ cal$ and $71030 \ cal$. What will be the heat of conversion of rhombic sulphur to monoclinic? $(cal)$

The reaction $CH_{4(g)} + Cl_{2(g)} \to CH_3Cl_{(g)} + HCl_{(g)}$ has $\Delta H = -25 \, kcal$. Given bond energies $BE(C-H) = 84 \, kcal$,$BE(H-Cl) = 103 \, kcal$,$BE(C-Cl) = x$,and $BE(Cl-Cl) = y$. If $\frac{x}{y} = \frac{9}{5}$,then find the value of $y$. (in $, kcal$)

Which of the following equations is used to calculate the standard enthalpy change of a reaction $(\Delta_r H^\circ)$?