Question

For the combustion of benzene to gaseous carbon dioxide and liquid water, $\Delta H$ is more than $\Delta U$.

• A. True
• B. False
• C. Ambiguous
• D. insufficient data

Answer 1

The correct option is B False

The balanced chemical equation for the combustion of benzene is $C_6{H}_6\left(l\right)+\frac{15}{2}{O}_2\left(g\right)\to 6C{O}_2\left(g\right)+3H_{2}O\left(l\right)$

The change in the number of moels of the gaseous reactants and the gaseous products is $\Delta n=6-\frac{15}{2}=-\frac{3}{2}$

The relationship between the enthalpy change $\Delta H$ and the change in the internal energy $\Delta U$ is

$\Delta H=\Delta U+\Delta nRT=\Delta U-\frac{3}{2}RT$

$\Delta H<\Delta U$

Thus, for the combustion of benzene to gaseous carbon dioxide and liquid water, $\Delta H$ is less than $\Delta U$.