GCSE-ready- Home
- Lessons
- GCSE & IGCSE Chemistry
- Rates of reaction
Rates of reaction
🎬 The doodle video for this lesson is coming soon. Subscribe on YouTube to see it first.
Some reactions are explosive, others take years. Five factors control how fast a reaction goes.
Measuring rate
mean rate = amount of product formedtime (or reactant used up ÷ time)
Measure gas volume with a gas syringe, mass loss on a balance, or time for a cross to disappear under a cloudy solution.
Measure gas volume with a gas syringe, mass loss on a balance, or time for a cross to disappear under a cloudy solution.
Factors
Rate increases with higher temperature, higher concentration (or pressure for gases), larger surface area (smaller pieces) and a catalyst.
Graphs
On a graph of product against time, a steeper gradient means a faster rate.
The line levels off when the reaction stops because a reactant has run out.
For a tangent to a curve (Higher), rate = gradient of the tangent.
The line levels off when the reaction stops because a reactant has run out.
For a tangent to a curve (Higher), rate = gradient of the tangent.
A reaction produces 60 cm3 of gas in 30 s. Find the mean rate.
- rate = 60 ÷ 30
Answer: 2 cm3/s
Rate = amount ÷ time. Temperature, concentration or pressure, surface area and catalysts all increase rate. A steeper graph means a faster reaction.
Check you have got it
Answer 6 quick questions with instant marking. If you get one wrong, GCSE-ready shows you why and gives you another go. It is free, and you do not need an account.