# Why would knowing the molar volume of a gas be important?

##### 1 Answer

The molar volume of a gas expresses the volume occupied by **1** mole of that respective gas under certain temperature and pressure conditions.

The most common example is the molar volume of a gas at **STP** (Standard Temperature and Pressure), which is equal to **22.4 L** for 1 mole of *any ideal gas* at a temperature equal to **273.15 K** and a pressure equal to **1.00 atm**.

So, if you are given these values for temperature and pressure, the volume occupied by any number of moles of an ideal gas can be easily derived from knowing that 1 mole occupies 22.4 L.

For 2 moles of a gas at STP the volume will be

For 0.5 moles the volume will be

The molar volume of a gas is derived from the ideal gas law

Let's say you were given a temperature of **355 K** and a pressure of **2.5 atm**, and asked to determine the gas' molar volume at these conditions. Since molar volume refers to the volume occupied by 1 mole, you'd get

This is how much volume 1 mole occupies at 355 K and 2.5 atm. It becomes clear that the volume occupied by any number of moles at these conditions can be easily determined:

As a conclusion, knowing a gas' molar volume at a certain temperature and a certain pressure can simplify the calculation of the volume occupied by any number of moles of that respective gas.

Good explanation, good figures here: http://chemwiki.ucdavis.edu/Textbook_Maps/General_Chemistry_Textbook_Maps/Map%3A_Lower%27s_Chem1/06._Properties_of_Gases/6.3%3A_Dalton%27s_Law