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Edexcel IGCSE Chemistry 1.36 Metal oxide formula practical

Practise using mass changes, repeated heating and gas-flow precautions to determine metal oxide formulae from combustion or reduction practicals.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • explain why a crucible lid is lifted so oxygen can react with heated magnesium
  • describe reheating and reweighing until constant mass to improve oxide mass results
  • apply hydrogen safety and cooling steps to stop hot reduced metal being reoxidised

1.36 Metal oxide formula practical question 1

[Maximum number: 4]

Question (a)

(a)

A student uses this apparatus to determine the formula of magnesium oxide.

Figure for Question (a) — Edexcel IGCSE Chemistry

This is the student's method.
- find mass of empty crucible and lid
- place some magnesium ribbon in crucible
- find mass of crucible, lid and magnesium ribbon
- heat crucible, lifting lid occasionally
- after five minutes, find mass of crucible, lid and magnesium oxide

[ 4 ]

Question (i)

(i)

Explain why the student lifts the lid.

[ 2 ]

Question (ii)

(ii)

The mass of magnesium oxide formed is less than expected.

Describe what the student should do next to obtain a more accurate value for the mass of magnesium oxide.

[ 2 ]
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