Molar Volume at STP

Molar Volume of a Gas at STP

As you may know, gases change volume (expand and contract) with changes in pressure and temperature.

To compare volume of gases we use a standard condition called STP(Standard Temperature and Pressure)

STP = 1 atmosphere of pressure and a temperature of 0C (or) 273.15K

If at STP, 1 mole of gas occupies 22.4L, therefore we can create these conversion factors:
22.4L of gas
----------------
1 mole of gas

(or)

1 mole of gas
-----------------
22.4L of gas

Examples:
1. What volume will 3.20 moles of 02 gas occupy at STP?

3.20moles x 22.4L
1 mole

3.20moles x 22.4L “moles cancel, left with litres”
1 mole

= 71.7L occupied by 3.20moles 02 gas

2. What volume will 0.500 moles of NH3 gas occupy at STP?

0.500moles x 22.4L
1 mole

0.500moles x 22.4L “moles cancel, left with litres”
1 mole

= 11.2L occupied by 0.0500moles NH3 gas

3. What volume will 60.00g of CO2 gas occupy at STP?

28.0g x 1mole x 22.4L
28g 1mol


44.0g x 1mole x 22.4L = 30.55L occupied by 60g CO2
44g 1mole
“first convert to moles, then use moles to calculate litres occupied”
= 3630L occupied by 9.758 x 1025 atoms of N2O5