# Ammonia gas occupies two containers. One volume is TWICE the volume of the other. Given that the containers are under the same pressure AND same temperature, how many molecules are in the second volume if the first volume contains 6xx10^23 particles?

The answer would be $3 \times {10}^{23}$.
Given the same temperature and pressure, $V \propto n$, where $n$ is the number of moles, i.e. the number of gaseous particles. We double the volume, and to maintain the equality we double the number of particles. This is even despite the enhanced intermolecular forces that operate in ammonia, which are due to what phenomenon?
This is Avogadro's gas law, and of course is also implicit in the ideal gas law, i.e. $n = \frac{P V}{R T} = k V$, where $P$ and $T$ are constant.