Question

When $1.0g$ of oxalic acid $\left(H_2{C}_2{O}_4\right)$ 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 $27{}^{\circ }C$ is:

• A. $-345.7kJ/mol$
• B. $-544.452kJ/mol$
• C. $-241.95kJ/mol$
• D. None of these

Answer 1

The correct option is C $-241.95kJ/mol$

The balanced chemical equation for the reaction is:
$H_2{C}_2{O}_4\left(s\right)+\frac{1}{2}{O}_2\left(g\right)\to H_{2}O\left(l\right)+2C{O}_2\left(g\right);\Delta n_g=2-\frac{1}{2}=\frac{3}{2}\Delta U_c=-\frac{0.312\times 8.75}{1}\times 90=-245.7kJ/mol\text{We know},\Delta H=\Delta U+\Delta n_{g}RT=-245.7+\frac{3}{2}\times \frac{8.314\times 300}{1000}=-241.95kJ/mol$