Edexcel IGCSE Chemistry Problem-solving and Application

Practise Edexcel IGCSE Chemistry problem-solving and application by explaining practical observations, excess reagents and measurement choices.

Exam points

Explain observations in a practical setup, such as bubbles caused by expanding air.
Use the idea of an excess reagent to justify why exact mass or volume is unnecessary.

Covered syllabus points

Solve problems in practical contexts Apply chemistry in practical contexts

[Maximum number: 1]

A student uses this apparatus to investigate the rate of reaction between dilute sulfuric acid and an excess of small pieces of zinc.

Figure for Question Problem-solving and application question 1 — Edexcel IGCSE Chemistry

This is the student's method.
Step 1 use $50 \mathrm{~cm}^{3}$ of dilute sulfuric acid
Step 2 add approximately 5 g of small zinc pieces to the sulfuric acid
Step 3 quickly connect the gas syringe
Step 4 record the reading on the gas syringe every 30 seconds until the reaction stops

Give a reason why the mass of zinc pieces does not need to be measured accurately.

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Covered syllabus points

Problem-solving and application question 1