Five moles of an ideal gas expands isothermally at 300 k from an initial volume of 100 l to a final volume of 500 l. calculate

The question is incomplete. But this is a typical thermodynamic problem. Looking at the given data and knowing that it is an isothermal process, the most probable question would be, the final pressure of the system. The solution is as follows:

For state 1,
PV=nRT
P₁(100 L)(1 m³/1,000 L) = (5 mol)(8.314 m³Pa/molK)(300 K)
P₁ = 124,710 Pa

For isothermal process:
P₁V₁ = P₂V₂
(124,710 Pa)(100 L)= P₂(500 L)
Solving for P₂,
P₂ = 24,942 Pa