A student is investigating how the volume of gas produced changes over time when zinc granules react with dilute sulfuric acid. The student collects the gas in a gas syringe and records the volume every 30 seconds. Describe how the student should carry out this investigation to obtain valid and reliable results, and explain how the results would show when the reaction has finished.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Zinc granules react with dilute sulfuric acid to produce zinc sulfate solution and hydrogen gas. The student wants to investigate how the volume of gas produced changes over time.
Model answer (5 marks)
1. Use the same fixed mass of zinc granules for each trial.
2. Use the same volume and concentration of dilute sulphuric acid each time.
3. Record the gas volume in the syringe at regular 30‑second intervals.
4. Repeat the experiment at least once more and calculate a mean to check for anomalies.
5. The reaction is finished when successive readings show no further increase in gas volume.
2. Use the same volume and concentration of dilute sulphuric acid each time.
3. Record the gas volume in the syringe at regular 30‑second intervals.
4. Repeat the experiment at least once more and calculate a mean to check for anomalies.
5. The reaction is finished when successive readings show no further increase in gas volume.
Examiner tips
- Use precise measurement tools (balance, pipette) to ensure consistency. Record data in a clear table with time and volume. Check for outliers before averaging.
- common_mistakes
- :
- Using different masses of zinc or acid volumes. Failing to record data at consistent time intervals. Not repeating the experiment to confirm reliability.
Mark scheme (5 marks)
- Measure and record a fixed/constant mass or amount of zinc granules for each repeat
- Measure and use the same volume and concentration of sulfuric acid each time
- Record the volume of gas in the syringe at regular time intervals (every 30 seconds)
- Repeat the experiment at least once more and calculate a mean / repeat to check for anomalous results
- The reaction has finished when the volume of gas in the syringe stops increasing / remains constant over successive readings
Key terms in this question
Related
- All OCR A-Level Chemistry B: Salters (H433) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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