A teacher adds a small piece of a Group 1 metal to a large bowl of water.
The teacher measures the time taken for the piece of metal to react completely. All the pieces are the same size.
The teacher does each experiment three times.
The table shows the results.
| Metal | Atomic radius (pm) | Time in trial 1 (s) | Time in trial 2 (s) | Time in trial 3 (s) |
|---|---|---|---|---|
| lithium | 152 | 70 | 74 | 72 |
| sodium | 186 | 17 | 30 | 19 |
| potassium | 227 | 4 | 5 | 3 |
Describe the trend in atomic radius down Group 1.
One of the results for sodium is anomalous.
Calculate the mean time for sodium. Do not include the anomalous result.
The mean time for lithium is 72 s. The mean time for potassium is 4 s.
Calculate how many times longer lithium takes to react than potassium.
Rubidium is below potassium in Group 1.
Predict the time taken for the same size piece of rubidium to react.
Explain your prediction.
Explain why the reactivity of the Group 1 metals increases down the group.
Use ideas about atomic radius and electrons.
Balance the symbol equation for the reaction of potassium with water.
...... K + ...... H₂O → ...... KOH + H₂
A student says:
"The atomic radius of potassium is about 1.5 times the atomic radius of lithium. So lithium takes about 1.5 times as long to react as potassium."
Evaluate the student's statement. Use the data.
60 exam-style questions on OCR GCSE Chemistry 4.1 Predicting chemical reactions, covering 4.1.1 Properties and trends in Groups 1, 7 and 0, 4.1.2 Properties of the transition metals, 4.1.3 Reactivity predicted from position in the Periodic Table, and 4.1.4 Reactivity of metals and the reactivity series. Each one has a worked solution and a mark scheme showing where the marks go.