Question

Under which of the following conditions is the relation,
$\Delta H=\Delta U+P\Delta V$
valid for a closed system.

• A. At constant pressure
• B. At constant volume
• C. At constant temperature
• D. At constant volume and pressure

Answer 1

The correct option is A At constant pressure

We know enthalpy change is given as:
$\Delta H=\Delta U+\Delta \left(PV\right)$
$\Delta H=\Delta U+P\Delta V+V\Delta P$
At constant pressure,
$\Delta P=0$,
so, $\Delta H=\Delta U+P\Delta V$