3.5.1 Amount of Substance in Relation to Volumes of Gases

Understanding Molar Gas Volume

infoNote

At room temperature (20°C) and standard pressure (1 atm), one mole of any gas occupies a volume of 24 dm³ (or 24,000 cm³). This is known as the molar gas volume. This relationship is useful because if you know the number of moles of a gas, you can easily calculate its volume, and vice versa.

Using the Molar Gas Volume to Calculate Volume

infoNote

To find the volume of a gas in dm³, use the formula:

Volume (dm^3)=Moles×24

If you need the volume in cm³, multiply the volume in dm³ by 1,000.

infoNote

Worked Example 1

Problem: Calculate the volume of 7.52 g of ammonia $(NH₃)$ gas at room temperature and pressure.

Calculate moles of NH₃:

Mr of NH_3=14 (N)+3×1 (H)=17

Moles of NH3= \frac{7.52 g}{17}=0.44 mol

Calculate volume:

Volume=0.44×24=10.56 dm^3

infoNote

Worked Example 2

Problem: 3.25 g of zinc (Zn) reacts with excess hydrochloric acid $(HCl)$ to form zinc chloride $(ZnCl₂)$ and hydrogen gas $(H₂)$ . Calculate the volume of hydrogen gas produced.

Calculate moles of zinc:

Moles of Zn= \frac{3.25 g}{65 (Mr of Zn)}=0.05 mol

Use mole ratio from the balanced equation: Since the ratio of $Zn$ to $H₂$ is 1:1, the moles of hydrogen gas produced will also be 0.05 mol.
Calculate the volume of hydrogen gas:

Volume=0.05×24=1.2 dm^3

Convert to cm³:

1.2×1000=1200 cm^3

Amount of Substance in Relation to Volumes of Gases Simplified Revision Notes for GCSE AQA Chemistry

3.5.1 Amount of Substance in Relation to Volumes of Gases

Understanding Molar Gas Volume

Using the Molar Gas Volume to Calculate Volume

500K+ Students Use These Powerful Tools to Master Amount of Substance in Relation to Volumes of Gases For their GCSE Exams.

Other Revision Notes related to Amount of Substance in Relation to Volumes of Gases you should explore