Question

A mixture of 2 mole of carbon monoxide and one mole of oxygen in a closed vessel is ignited to get carbon dioxide. If $\Delta H$ is the enthalpy change and $\Delta U$ is the change in internal energy, then:

• A. $\Delta H>\Delta U$
• B. $\Delta H<\Delta U$
• C. $\Delta H=\Delta U$
• D. can't be predicted

Answer 1

Answer: (B)

$\Delta H<\Delta U$

A mixture of 2 moles of carbon monoxide and one mole of oxygen in a closed vessel is ignited to get carbon dioxide.

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

$\Delta n_g=2-3=-1$

If $\Delta H$ is the enthalpy change and $\Delta U$ is the change in internal energy, then:

$\Delta H=\Delta U+\Delta n_{g}RT=\Delta U-RT$

Hence, $\Delta H<\Delta U$