IGCSEChemistryOxford AQARevision NotesQuantitative ChemistryUsing Molar Concentrations of Solutions & Amount of Substance In Relation to Volumes of GasesGas Volumes

Gas Volumes (Oxford AQA IGCSE Chemistry)

Revision Note

Philippa Platt

Written by: Philippa Platt

Reviewed by: Stewart Hird

Calculating Gas Volumes

  • At room temperature and pressure, the volume occupied by one mole of any gas was found to be 24 dm3 or 24,000 cm3

  • This is known as the molar gas volume at rtp:

    • RTP stands for room temperature and pressure

  • From the molar gas volume the following formula triangle can be derived by:

Formula triangle for calculating molar gas volume in dm3

molar-gas-volume- triangle for calculations in dm3
Formula triangle showing the relationship between moles of gas, volume in dm3 and the molar volume

Formula triangle for calculating molar gas volume in cm3

molar-gas-volume- triangle for calculations in dm3
Formula triangle showing the relationship between moles of gas, volume in cm3 and the molar volume

Worked Example

Convert the following moles of gases at rtp into volume (dm3)

  1. 3 moles of hydrogen

  2. 0.25 moles of carbon dioxide

  3. 5.4 moles of oxygen

  4. 0.02 moles ammonia

Answer:

Use the equation:

volume = moles x 24

  1. 3 x 24 = 72 dm3

  2. 0.25 x 24 = 6 dm3

  3. 5.4 x 24 = 129. 6 dm3

  4. 0.02 x 24 = 0.48 dm3

Worked Example

Convert the following volumes of gases at rtp into moles

  1. 225.6 dm3 methane

  2. 7.2 dm3 carbon monoxide

  3. 960 cm3 sulfur dioxide

  4. 1200 cm3 of oxygen

Answer:

Use the equation :

moles = volume (dm3) ÷ 24

OR

moles = volume (cm3) ÷ 24 000

  1. 225.6 ÷ 24 = 9.4 mols

  2. 7.2 ÷ 24 = 0.3 mols

  3. 960 ÷ 24 000 = 0.04 mols

  4. 1200 ÷ 24 000 = 0.05 mols

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    Philippa Platt

    Author: Philippa Platt

    Expertise: Chemistry

    Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener

    Stewart Hird

    Author: Stewart Hird

    Expertise: Chemistry Lead

    Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.