Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
The combustion of elements in oxygen
18 practice questions
Practice questions
11–18 of 18
Question 11
2 marks · Normal
Answer and see the solution →Suggest one reason why some elements burn more brightly in pure oxygen than in air. Name an element that burns brightly in oxygen.
Question 12
4 marks · Normal
Answer and see the solution →Sulfur burns in oxygen to make a new substance.
(a)[1 mark]Describe what you would see when sulfur is burned in oxygen.
(b)[1 mark]Write a balanced chemical equation for the reaction between sulfur and oxygen.
(c)[1 mark]Name the product formed.
(d)[1 mark]Briefly explain why burning sulfur in oxygen is a combustion reaction.
Question 13
3 marks · Normal
Answer and see the solution →When magnesium burns in oxygen, it forms magnesium oxide. Student A burns 1.2 g of magnesium in excess oxygen. The equation is:
Calculate the mass of magnesium oxide formed. (Relative atomic masses: Mg = 24, O = 16)
Question 14
3 marks · Normal
Answer and see the solution →Sodium burns with a bright yellow flame when heated in oxygen. Explain, with reference to the reaction, why the flame is brighter and the reaction is faster when sodium is heated in pure oxygen, compared to heating it in air.
Question 15
4 marks · Normal
Answer and see the solution →The diagram below shows a scientist burning a piece of magnesium in a bell jar filled with air. The bell jar is placed over a trough of water. After ignition, the magnesium burns in oxygen to form magnesium oxide.
Burning magnesium in a bell jar over water. Measured water volumes used to fill the bell jar to marked levels before and after reaction. Water level Volume / cm³ Initial 695 Final 830 After burning, the white magnesium oxide forms and dissolves in the water. The levels of water inside the bell jar before and after combustion are shown in the table.
(a)[1 mark]State one observation you would see when magnesium reacts with oxygen in this experiment.
(b)[1 mark]Calculate the volume of oxygen that was used up during the reaction. Show your working.
(c)[1 mark]Given that the total volume of air in the bell jar at the start was 695 cm³, calculate the percentage of oxygen in the air based on your answer to (b). Show your answer to two significant figures.
(d)[1 mark]Explain why there might still be some magnesium left after the experiment.
Question 16
2 marks · Hard
Answer and see the solution →Explain why a strip of iron wool burns more vigorously in pure oxygen than in air.
Question 17
5 marks · Hard
Answer and see the solution →Sodium and magnesium both burn in oxygen, forming new compounds. The reactions are more vigorous in pure oxygen than in air.
(a)[1 mark]Write a balanced chemical equation for the reaction of sodium with oxygen.
(b)[2 marks]Describe what you would observe when magnesium burns in pure oxygen.
(c)[2 marks]Explain, using ideas about the percentage of oxygen in air, why sodium and magnesium burn more vigorously in pure oxygen than in air.
Question 18
2 marks · Hard
Answer and see the solution →Describe what is meant by a combustion reaction, and give one example of such a reaction involving an element.