# A container has a volume of 3 L and holds 1 mol of gas. If the container is expanded such that its new volume is 8 L, how many moles of gas must be injected into the container to maintain a constant temperature and pressure?

$\frac{5}{3}$ moles
Hence the equation $P V = n R T$ can be applied.
Now the volume is increased by a factor of $\frac{8}{3}$ $\therefore$ number of moles should also increase by a factor of $\frac{8}{3}$
$\therefore$ new number of moles $= 1 \times \frac{8}{3} = \frac{8}{3}$
$\therefore$ extra moles which we have to inject are $\frac{8}{3} - 1 = \frac{5}{3}$ moles