The combustion of elements in oxygen
3 marks · EasyThe diagram shows an experiment in which sulfur is burned in a bell jar filled with air over a trough of water.
Describe what you would see when sulfur burns in oxygen.
Write a word equation for the reaction of sulfur and oxygen.
Explain why the water level inside the bell jar rises after burning sulfur, based on the changes taking place inside the jar.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) A blue flame is observed and a colourless gas forms (sometimes with a choking smell).
(b) sulfur + oxygen → sulfur dioxide
(c) Oxygen is used up during combustion, so the volume of gas in the jar decreases and water rises to fill the space left by the oxygen.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States that a blue flame is seen or mentions the formation of a colourless (choking) gas.
B1 (b) · 1 mark · Correct word equation: sulfur + oxygen → sulfur dioxide.
B1 (c) · 1 mark · Explains that oxygen is used up in the reaction so water rises to fill the space left by the oxygen.
Worked solution
a) When sulfur burns in oxygen, a blue flame is seen and a colourless gas is produced.
b) sulfur + oxygen → sulfur dioxide
c) The water level rises because oxygen is used up when sulfur combusts, decreasing the gas volume in the jar. Water replaces the removed oxygen.