When 1.0 gr of oxalic acid (H₂C₂O₄) is burned in a bomb calorimeter whose heat capacity is 8.75kJ/K, the temperature increases by 0.312K. The enthalpy of combustion of oxalic acid at 27°C.

In a bomb calorimeter, We can calculate $∆$U which is equal to Q
$\begin{array}{l}\mathrm{Q}=\mathrm{\Delta U}=-\mathrm{ms\Delta T}=-8.75\times 0.312=-2.73/\mathrm{gr}\\ \mathrm{\Delta U}\text{ per mole }=-2.73\times 90=-245.7\mathrm{kJ}\\ \mathrm{\Delta H}=\mathrm{\Delta U}+{\mathrm{\Delta n}}_{\mathrm{g}}\mathrm{RT}\end{array}$
Reaction for combustion of oxalic acid
$$\begin{gathered} \begin{array}{l}{\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_{4_{\left(\mathrm{s}\right)}}+\frac{1}{2}{\mathrm{O}}_{2_{\left(\mathrm{g}\right)}}⟶2{\mathrm{CO}}_{2_{\left(\mathrm{g}\right)}}+{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{\ell }\right)}{\mathrm{\Delta n}}_{\left(\mathrm{g}\right)}=\frac{3}{2}\\ \mathrm{\Delta H}=-245.7+\frac{3}{2}\times 8.314\times {10}^{-3}\times 300=-241.9587\mathrm{kJ}/\mathrm{mole}\\ \mathrm{\Delta H}=-58.51+\frac{3}{2}\times {10}^{-3}\times 2\times 300=-57.87\mathrm{kcal}/\mathrm{mole} \end{array} \\ (1\mathrm{Joule}=0.238 \mathrm{cal}) \end{gathered}$$