Revision notes · Quantitative chemistry
Use of amount of substance in relation to volumes of gases
Use of amount of substance in relation to volumes of gases4.3.5
Definition: The molar gas volume is the volume occupied by one mole of any gas at room temperature and pressure, which is 24 dm³.
Equal amounts of any gas occupy the same volume under identical conditions of temperature and pressure.
- •At room temperature (20 °C) and pressure (1 atm), one mole of any gas occupies 24 dm³ (or 24,000 cm³).
- •The volume of a gas is calculated using the formula: volume of gas (dm³) = amount (mol) × 24.
- •To convert a gas volume from cm³ to dm³, divide the value by 1000.
- •In balanced chemical equations, the molar ratio of reacting gases is equal to the ratio of their volumes.
⚠️ Common mistake: Forgetting to convert volumes from cm³ to dm³ (by dividing by 1000) before applying the molar gas volume equation.
🧠 Remember: Volume (dm³) = Moles × 24
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