Question 1 Medium
Hydrogen peroxide is broken down using manganese dioxide. The gas relights a glowing splint. Name the gas.
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Answer: oxygen
- A gas that relights a glowing splint is oxygen.
- The manganese dioxide is the catalyst.
Tests for gases: GCSE Combined Science Chemistry practice questions
A second set of questions on tests for gases. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
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Question 2 Medium
Should the litmus paper be dry or damp for the chlorine test?
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Answer: damp
- Chlorine bleaches litmus paper only when it is damp.
- So the paper is damp.
Question 3 Hard
Limewater turns milky. Name the white solid that makes it milky.
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Answer: calcium carbonate
- Carbon dioxide reacts with calcium hydroxide.
- The products are calcium carbonate and water. The calcium carbonate is the white solid.
Question 4 Hard
A student collects a gas that gives a squeaky pop. What is made when this gas burns in air?
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Answer: water
- The gas is hydrogen.
- Hydrogen burns with oxygen to make water.
Question 5 Hard
Which gas is toxic and bleaches damp litmus paper white?
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Answer: chlorine
- Bleaching damp litmus paper is the chlorine test.
- Chlorine is also poisonous.
Question 6 Hard
What is the formula of the gas that turns limewater milky?
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Answer: CO₂
- Limewater is turned milky by carbon dioxide.
- The formula is CO₂.
Question 7 Hard
Name the two gases made when sodium chloride solution is electrolysed.
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Answer: hydrogen and chlorine
- Hydrogen forms at the negative electrode.
- Chlorine forms at the positive electrode.
Question 8 Hard
A gas does not change limewater and does not relight a glowing splint. A lit splint gives a squeaky pop. Name the gas.
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Answer: hydrogen
- The squeaky pop is the hydrogen test.
- The gas is hydrogen.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What is the test for hydrogen gas?
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Hold a lit splint at the open end of a test tube of the gas. A squeaky pop shows hydrogen.
Check 2
What is the test for oxygen gas?
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Put a glowing splint in the gas. It relights if the gas is oxygen.
Check 3
What is the test for carbon dioxide gas?
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Bubble the gas through limewater. It turns milky (cloudy) if the gas is carbon dioxide.
Check 4
What is the test for chlorine gas?
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Hold damp litmus paper in the gas. It is bleached white if the gas is chlorine.
Check 5
What gas is made when a metal reacts with an acid?
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Hydrogen.
Check 6
What gas is made when a carbonate reacts with an acid?
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Carbon dioxide.
Check 7
What is limewater?
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A clear solution of calcium hydroxide.
Check 8
What makes limewater go milky?
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Calcium carbonate, a white solid that forms when carbon dioxide reacts with limewater.
Check 9
What is made when hydrogen burns in air?
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Water.
Check 10
Why must litmus paper be damp for the chlorine test?
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Chlorine bleaches damp litmus paper. Dry paper is not bleached.
Check 11
What colour and smell does chlorine have?
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Chlorine is a pale green gas with a sharp, choking smell.
Check 12
What is the hazard of chlorine gas?
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It is toxic (poisonous) and irritates the eyes and lungs.
Check 13
Where should the chlorine test be done?
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In a fume cupboard, using a small amount of gas.
Check 14
Why is hydrogen a hazard?
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It is flammable and can explode with air.
Check 15
What is the formula of hydrogen gas?
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H₂.
Check 16
What is the formula of oxygen gas?
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O₂.
Check 17
What is the formula of carbon dioxide?
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CO₂.
Check 18
What is the formula of chlorine gas?
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Cl₂.
Check 19
What gas is made when hydrogen peroxide breaks down with manganese dioxide?
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Oxygen. The manganese dioxide is a catalyst.
Check 20
Which gases are made when sodium chloride solution is electrolysed?
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Hydrogen at the negative electrode and chlorine at the positive electrode.
Check 21
What fraction of air is oxygen?
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About one fifth (21%).
Check 22
Does a burning splint going out prove a gas is carbon dioxide?
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No. Other gases also put out a flame. Use limewater.
Check 23
What should you write in a gas test answer?
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The test and the positive result.
Check 24
Which gas turns damp litmus paper white?
Show answer
Chlorine.
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