Mass to Volume Conversion

- At a specific pressure and temperature one mole of any gas occupies the same volume.

- At 0 degrees Celsius and 101.3 kilo Pascals 1 mol = 22.4 L

- This temperature and pressure is called STP

- 22.4 L/ mol is the molar volume at STP

Example:

How many litres will 2.5 mol of hydrogen gas occupy at STP

1) 2.5 mol hydrogen gas = 22.4 L/ 1 mol = 556 L

litres to mols

2) 11.6 L = 1 mol/ 22.4 L = 0.518 mol

Example:

At STP a sample of oxygen gas contains 11.5 mol.
How many litres of oxygen gas are there?

11.5 mol = 22.4 L/ 1 mol = 258 L

150ml x 1 L/ 1000 ml = 0.15 L

0.15 L x 1 mol/ 22.4 L = 0.00670 mol

Extra Notes:
-In conversions mols will almost always equal 1
-Remember to convert values to the appropriate units when asked for a different unit
-Also remember to use significant figures because these are very important in conversions