Question

$H_2\left(g\right)+1/2O_2\left(g\right)⟶H_{2}O\left(l\right)$
Which of the following alternative is correct?

• A. $\Delta H=\Delta U$
• B. $\Delta H>\Delta U$
• C. $\Delta H<\Delta U$
• D. $\Delta Hand\Delta U$ bear no relation with each other

Answer 1

The correct option is C $\Delta H<\Delta U$

As we know,
$\Delta H$ =$\Delta U+\Delta n_{g}RT$
here,
$H_2\left(g\right)+1/2O_2\left(g\right)⟶H_{2}O\left(l\right)$
$\Delta n_g=-3/2$
so,
$\Delta H$ < $\Delta U$