AQA GCSE Chemistry

Topic Questions

GCSEChemistryAQATopic Questions8. Chemical Analysis8.2 Identification of Common Gases

8.2 Identification of Common Gases

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11 mark

During the electrolysis of brine, chlorine gas forms at one electrode.

2Cl- (aq) rightwards arrowCl2 (g) + 2e-

Which test would be most appropriate to confirm that chlorine gas was produced?

  • Collect the gas and see if it extinguishes a glowing splint

  • Collect the gas and check if it is green

  • Collect the gas and see if it bleaches damp litmus paper

  • Collect the gas and check if it smells of swimming pools

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21 mark

Which is the correct method for testing for hydrogen gas?

  • Hold the tube containing the gas upright and place a lit splint at the end of the tube

  • Hold the tube containing the gas upright and place a glowing splint at the end of the tube

  • Hold the tube containing the gas angled down and place a lit splint at the end of the tube

  • Hold the tube containing the gas angled down and place a glowing splint at the end of the tube

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31 mark

Which is not true about the test for carbon dioxide gas?

  • The gas is bubbled through limewater solution

  • Limewater is calcium hydroxide solution

  • The solution will turn cloudy due to the formation of a white precipitate

  • The colour will fade after a few minutes

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41 mark

What is the correct observation when a glowing splint is held at the entrance of a tube of pure oxygen gas? 

  • A 'squeaky pop' sound can be heard

  • The glowing splint relights

  • The glowing splint keeps glowing

  • The glowing splint is immediately extinguished

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51 mark

The electrolysis of fresh water produces hydrogen gas and oxygen gas.

The electrolysis of salt water (brine) produces hydrogen gas and chlorine, and leaves a solution of sodium hydroxide.

Which test would not help to identify a sample as being fresh water or salt water?

  • A gas collected makes a 'squeaky pop' when a lit splint is held in it

  • A gas collected relights a glowing splint

  • A gas collected bleaches damp litmus paper

  • The pH of the solution increases

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