# Question #5bf20

May 18, 2015

What you are thinking of is the concentration of a gas , which is dependent upon both temperature and pressure.

Concentration is a ratio of number of moles divided by the volume.

$\left[X\right] =$Concentration of X

$\left[X\right] = \frac{m o l X}{v o l u m e}$

For a gas the concentration can be changed by temperature and pressure (remember the gas laws) because both temperature and pressure impact the volume of the gas. In other words, the number of moles remains constant, but the temperature and pressure determine the distance between the gas particles.

At standard temperature and pressure (STP)one mole of any gas has a volume (if held constant) of 22.4 L (or 22,400 mL)

A gas is at STP at a temperature of 0 degrees Celsius, and a pressure of 1 bar (approximately 1 atm.)