Question 3
FA student heats some magnesium ribbon in a crucible with a lid.
The magnesium reacts with oxygen from the air to make magnesium oxide, a white powder.
The student lifts the lid a little from time to time during heating.
The diagram shows the apparatus the student uses.
The table shows the student's results.
| Measurement | Mass (g) |
|---|---|
| empty crucible and lid | 25.40 |
| crucible, lid and magnesium before heating | 25.64 |
| crucible, lid and magnesium oxide after heating | 25.80 |
a.[1]
Suggest why the student lifts the lid a little from time to time.
b.[1]
Calculate the mass of magnesium used.
Mass of magnesium = ...... g
c.[1]
Calculate the mass of magnesium oxide made.
Mass of magnesium oxide = ...... g
d.[2]
Calculate the mass of oxygen that reacted with the magnesium.
Name the law you used to work out your answer.
e.[2]
The mass of the crucible and its contents increases during the experiment.
Explain why. Use ideas about particles.
f.[1]
Balance the equation for the reaction.
...... Mg + O₂ → ...... MgO
g.[2]
The student repeats the experiment without a lid. Some white smoke escapes from the crucible.
Predict how this changes the mass of magnesium oxide the student measures.
Explain your answer.
3.1 Introducing chemical reactions Questions
55 exam-style questions on OCR GCSE Chemistry 3.1 Introducing chemical reactions, covering 3.1.1 Writing formulae and balanced chemical equations, 3.1.2 Formulae of compounds from ions, and state symbols, 3.1.3 Conservation of mass and observed changes in mass, 3.1.4 Half equations and balanced ionic equations, 3.1.5 The mole and the Avogadro constant, and 3.1.6 Stoichiometry, limiting reactants and reacting masses. Each one has a worked solution and a mark scheme showing where the marks go.