Question

A mixture of $2$ mole of $CO\left(g\right)$ and one mole of $O_2$, in a closed vessel, is ignited to convert the carbon monoxide to carbon dioxide. If $\Delta H$ and $\Delta U$ are enthalpy and internal energy change, then:

• A. $\Delta H<\Delta U$
• B. $\Delta H>\Delta U$
• C. $\Delta H=\Delta U$
• D. the relationship depends on the capacity of the vessel

Answer 1

Answer: (A)

$\Delta H<\Delta U$

$2CO\left(g\right)+O_2\left(g\right)⟶2{CO}_2\left(g\right)$

${\Delta n}_g=2-2-1=-1$

$\Delta H=\Delta U+{\Delta n}_{g}RT$

$\therefore \Delta H=\Delta U-RT$

$\therefore \Delta H<\Delta U$