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Question 27

This question is about some gases and the combustion of hydrocarbons.

a.

What is the test for oxygen?

[2]
b.

Methane gas (CH4\text{CH}_4CH4​) is burned in air. The diagram below shows the experimental setup used to collect and test the products of combustion.

A burner with burning methane gas. Above the flame, a funnel collects the rising combustion gases into an inverted delivery tube. The tube leads into a U-shaped tube cooled in an ice-water bath, where a colourless liquid collects. The delivery tube then leaves the U-shaped tube and bubbles through a conical flask containing limewater, before connecting to a suction pump. The limewater in the conical flask turns cloudy rapidly.

A colourless liquid collects in the U-shaped tube and the limewater turns cloudy rapidly.

Describe a chemical test to show that the colourless liquid contains water.

  • Test:
  • Result:
[2]
c.

Describe a physical test to show that the colourless liquid is pure water.

  • Test:
  • Result:
[2]
d.

The reaction in the conical flask causes the limewater to turn cloudy quickly. Which two of the following statements are correct?

  • Methane combustion produces carbon dioxide gas.
  • Carbon dioxide from the air is the main reason the limewater turns cloudy quickly.
  • The cloudiness is caused by the formation of an insoluble white precipitate of calcium carbonate.
  • The cloudiness is caused by the formation of soluble calcium hydroxide.
  • The reaction in the limewater represents an oxidation reaction.
[2]

Chemical tests Questions

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