Edexcel IGCSE Chemistry Accuracy and Validity

Edexcel IGCSE Chemistry Accuracy and Validity
Edexcel IGCSE Chemistry syllabusChemistry 4CH1Issue 3 (2024)

Practise Edexcel IGCSE Chemistry accuracy and validity by explaining gas loss, timing errors and changes that improve practical measurements.

How this is tested

  • Explain how stirring or measuring both solution temperatures improves temperature accuracy.
  • Identify gas loss from late syringe connection as a reason for lower measured gas volume.
  • Suggest timing or reading errors that could cause anomalous practical results.

Question 4(d)(iv)

[Maximum number: 1]

A solution of hydrogen peroxide decomposes when a catalyst of manganese(IV) oxide is added.

The products of the reaction are water and oxygen.

A student investigates how changing the concentration of the hydrogen peroxide solution affects the rate of this reaction.

She uses this apparatus.

The student records the volume of oxygen that collects every 2 minutes for 16 minutes.
The table shows her results.

Time / minutes0246810121416
Volume of oxygen / cm302238505569768080
Figure for Question 4(d)(iv) — Edexcel IGCSE Chemistry
Table for Question 4(d)(iv) — Edexcel IGCSE Chemistry

Suggest a mistake that the student might have made to cause the anomalous result.