Question

Define the term 'enthalpy'.
What will happen to the internal energy if work is done by the system?

Answer 1

The enthalpy of a system is defined as the sum of the internal energy of the system and the energy taht arises due to its pressure and volume. Mathematically
$H=U+PV$
Here, H is enthalpy, U is the internal energy, P is pressure and V is volume.
Enthalpy is a state function.
Work done by the system is negative, $W<0$ .
$\Delta U=q+W$
When $W<0$, $\Delta U$ decreases.
The internal energy will decrease if work is done by the system.