If $2$ mole of an ideal gas expand isothermally and reversibly at $27^\circ$C from 1 $\text{dm}^3$ to $1\ \text{m}^3$ calculate work done? $[R = 8.314\ \text{J K}^{-1}\text{mol}^{-1}]$

Identify the law for the statement "Overall the enthalpy change for a reaction is equal to sum of enthalpy changes of individual steps in the reaction"

Calculate $\triangle G^\circ$ for reaction,
$\text{CH}_{4(g)} + \text{H}_{2(g)} \rightarrow \text{C}_2\text{H}_{6(g)}$ ($K_p = 2 \times 10^{17}$, $R = 8.314\ \text{JK}^{-1}\text{mol}^{-1}$)

Calculate the work done in the oxidation of one mole $\mathrm{HCl}_{(\mathrm{g})}$ at $27^{\circ} \mathrm{C}$, according to reaction.

$$ \begin{aligned} & 4 \mathrm{HCl}_{(\mathrm{g})}+\mathrm{O}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{Cl}_{2(\mathrm{~g})}+2 \mathrm{H}_2 \mathrm{O}_{(\mathrm{g})} \\ & \left(\mathrm{R}=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right) \end{aligned} $$