This introduction covers The Universal Gas Constant within Gas Volume for GCSE Chemistry. Topic 19: Gas Volume It is section 1 of 11 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 1 of 11
Practice
20 questions
Recall
20 flashcards
📖 The Universal Gas Constant
Think of gas particles as bouncing balls in a balloon. At room conditions, what matters isn't the SIZE of the balls, but how many there are and how fast they bounce. Since one mole always means the same NUMBER of particles (6.02 × 10²³), and they're all bouncing at the same speed (same temperature), they take up the same space — 24 dm³. Simple!
Why is this true? At the molecular level, gas particles are so far apart that their actual size doesn't matter — what matters is how many particles there are and how fast they're moving. Since temperature and pressure control this, and since a mole always means the same NUMBER of particles (6.02 × 10²³), one mole of any gas takes up the same space.
The molar gas volume at RTP (room temperature and pressure — 20°C and 1 atmosphere) is 24 dm³/mol or equivalently 24,000 cm³/mol.
This gives us a beautifully simple equation:
or
Moles = Volume (dm³) ÷ 24