Question

Which of the following is true for the value of $\Delta H - \Delta U$ at constant volume?

• A. R
• B. Zero
• C. $\frac{3}{2}R$
• D. $\frac{5}{2}R$

Answer 1

Answer: (A)

R

Answer 2

At constant volume for an ideal gas:

$\Delta H = \Delta U + \Delta(PV)$

Since $PV = nRT$, we have:

$\Delta(PV) = nR\Delta T$

Thus:

$\Delta H - \Delta U = nR\Delta T$

Assuming the process involves 1 mole and a unit temperature change, the expression becomes:

$\Delta H - \Delta U = R$