# Simple Ideal Gas problem

## Homework Statement

Determine the number density of particles in a gas at STP (T=273, p=1atm)

pV=nRT

Andrew Mason
Homework Helper

## Homework Statement

Determine the number density of particles in a gas at STP (T=273, p=1atm)

## The Attempt at a Solution

pV=nRT

It means the number of gas molecules per unit volume. Mass density is mass per unit volume. For a gas, the pressure and volume depends on the number of molecules, not their mass.

How many molecules of gas are then in a mole of the gas? How much volume does a mole of gas occupy at STP?

AM

hmm I can't quite get the right answer. V=22.4L and avagadros # is the molecules in one mole. How do I piece this together?

hmm I can't quite get the right answer. V=22.4L and avagadros # is the molecules in one mole. How do I piece this together?

Be careful of units here... when using PV=nRT what is the units of volume?

So you know Avogadro's # is the number of molecules in one mole... so put the pieces together. As Andrew said, the number density the number of gas molecules per unit volume