A reaction between two colourless solutions forms a suspended solid. A light sensor records the time taken for the mixture to reach a fixed cloudiness.
For this method, the rate of reaction is proportional to 1÷time1 \div \text{time}1÷time.
Fresh samples were tested at three temperatures. All other conditions were kept the same.
| Temperature in ∘C^\circ\text{C}∘C | Time to reach the fixed cloudiness in s\text{s}s |
|---|---|
| 15 | 90 |
| 30 | 50 |
| 45 | 30 |
Calculate how many times greater the rate of reaction is at 45 ∘C45\ ^\circ\text{C}45 ∘C than at 15 ∘C15\ ^\circ\text{C}15 ∘C.
A technician concludes:
‘Every increase of 15 ∘C15\ ^\circ\text{C}15 ∘C doubles the rate of reaction.’
Evaluate the technician's conclusion using the results.
Explain why increasing the temperature decreases the time taken to reach the fixed cloudiness.
127 exam-style questions on AQA GCSE Chemistry 6.1 Rate of reaction, covering 6.1.1a Calculating rates of reactions, 6.1.1b Gradient of a tangent as rate, 6.1.2 Factors which affect the rates of chemical reactions, 6.1.3 Collision theory and activation energy, and 6.1.4 Catalysts. Each one has a worked solution and a mark scheme showing where the marks go.