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Tests for gases

OCR GCSE Combined Science

Topic questions Chemical analysis Tests for gases

Tests for gases

10 questions · 80 marks · about 1.5 hours

Tests for gases questions

TopicTests for gases

Chemistry Paper 4 June 2025 Foundation tier, Question 16, also on the Higher paper 12 marks

Hydrogen peroxide solution, H₂O₂(aq), decomposes to make water and oxygen gas.

(a)

Complete the balanced symbol equation for the reaction.

$Question 16, shown as an image$

[2]

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(b)

Describe a test and its result which shows that the gas produced in the reaction is oxygen.

Test........

Result........

[2]

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(c)

A hydrogen peroxide solution produces oxygen gas slowly.

A student adds a piece of potato to the hydrogen peroxide solution. The potato contains a biological catalyst.

(c)(i)

What name is given to biological catalysts?

[1]

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(c)(ii)

Describe and explain the effect of adding the piece of potato to the hydrogen peroxide solution.

Include ideas about rate of reaction and activation energy.

[2]

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(c)(iii)

The student measures the total volume of oxygen produced in the reaction with and without the piece of potato.

With the potato, the total volume is: increased, decreased, stays the same.

Tick (✓) one box.

$Question 16, shown as an image$

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(d)

The piece of potato added to the hydrogen peroxide solution is a six-sided cube.

(d)(i)

Calculate the surface area of the piece of potato in cm². (i)

[2]

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(d)(ii)

A student thinks that cutting the potato into smaller pieces will make the catalyst more effective.

Explain why the student is correct.

Tick (✓) one box.

$Question 16, shown as an image$

[1]

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(e)

The student measures the rate of reaction when the piece of potato is added to the hydrogen peroxide.

The rate of reaction is 1.5 cm³ / s.

They then measure the rate of reaction again with an increased concentration of hydrogen peroxide.

What would the rate of reaction be now?

Tick (✓) one box.

$Question 16, shown as an image$

[1]

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Chemistry Paper 9 June 2025 Higher tier, Question 15 13 marks

Sodium hydroxide, NaOH, and calcium hydroxide, Ca(OH)₂, are ionic compounds that dissolve in water to form alkaline solutions.

(a)

Why are solutions of sodium hydroxide and calcium hydroxide called alkalis?

[1]

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(b)

Explain why the formula of sodium hydroxide is NaOH but the formula of calcium hydroxide is Ca(OH)₂.

[3]

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(c)

The electrolysis of a sodium hydroxide solution produces hydrogen at the cathode rather than sodium.

Explain why.

[3]

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(d)

When carbon dioxide is bubbled through a calcium hydroxide solution it turns cloudy white.

This is the equation for the reaction.

$Question 15, shown as an image$

(d)(i)

Which chemical in the equation turns the solution cloudy white?

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(d)(ii)

What is the alternative name for the calcium hydroxide solution?

[1]

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(d)(iii)

The calcium hydroxide solution contains 0.038 g of calcium hydroxide.

Calculate the maximum mass of carbon dioxide that can react with the calcium hydroxide solution.

Give your answer to 2 significant figures.

Relative atomic mass (A_r): H = 1.0 C = 12.0 O = 16.0 Ca = 40.1

[4]

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Chemistry Paper 10 June 2025 Higher tier, Question 11, also on the Foundation paper 12 marks

Hydrogen peroxide solution, H₂O₂(aq), decomposes to make water and oxygen gas.

(a)

Complete the balanced symbol equation for the reaction.

$Question 11, shown as an image$

[2]

Reveal mark scheme

(b)

Describe a test and its result which shows that the gas produced in the reaction is oxygen.

Test........

Result........

[2]

Reveal mark scheme

(c)

A hydrogen peroxide solution produces oxygen gas slowly.

A student adds a piece of potato to the hydrogen peroxide solution. The potato contains a biological catalyst.

(c)(i)

What name is given to biological catalysts?

[1]

Reveal mark scheme

(c)(ii)

Describe and explain the effect of adding the piece of potato to the hydrogen peroxide solution.

Include ideas about rate of reaction and activation energy.

[2]

Reveal mark scheme

(c)(iii)

The student measures the total volume of oxygen produced in the reaction with and without the piece of potato.

With the potato, the total volume is: increased, decreased, stays the same.

Tick (✓) one box.

$Question 11, shown as an image$

[1]

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(d)

The piece of potato added to the hydrogen peroxide solution is a six-sided cube.

(d)(i)

Calculate the surface area of the piece of potato in cm². (i)

[2]

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(d)(ii)

A student thinks that cutting the potato into smaller pieces will make the catalyst more effective.

Explain why the student is correct.

Tick (✓) one box.

$Question 11, shown as an image$

[1]

Reveal mark scheme

(e)

The student measures the rate of reaction when the piece of potato is added to the hydrogen peroxide.

The rate of reaction is 1.5 cm³ / s.

They then measure the rate of reaction again with an increased concentration of hydrogen peroxide.

What would the rate of reaction be now?

Tick (✓) one box.

$Question 11, shown as an image$

[1]

Reveal mark scheme

Chemistry Paper 3 June 2024 Foundation tier, Question 3 1 mark

Which gas turns limewater cloudy?

A Carbon dioxide

B Chlorine

C Hydrogen

D Oxygen

$Question 3, shown as an image$

[1]

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Chemistry Paper 3 June 2023 Foundation tier, Question 11 8 marks

(a)

Fig. 11.1 shows the particle model for an element.

Fig. 11.1

Solid Liquid Gas

(a)(i)

Complete Fig. 11.1 by drawing in the particles of the element when it is a gas.

[1]

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(a)(ii)

Describe how the particles of the element move in a solid.

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(a)(iii)

Name the change of state labelled X on Fig. 11.1.

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(b)

The table shows the state of the element chlorine at three different temperatures.

State of chlorine	Temperature (°C)
solid	–165
liquid	–90
gas	–20

Use the information in the table to estimate the melting point of chlorine.

Tick (✓) one box.

[1]

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(c)

A particle of chlorine has the formula Cl₂.

Fig. 11.2 shows some of the outer electrons in a particle of chlorine.

Fig. 11.2

(c)(i)

Complete Fig. 11.2 by drawing in the missing outer electrons.

[1]

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(c)(ii)

Complete the sentences about the bonding in a particle of chlorine.

$Question 11, shown as an image$

The particles of chlorine are called isotopes / molecules / polymers.

The atoms of chlorine are joined together by a covalent / ionic / metallic bond.

[2]

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(d)

Which test is used to identify chlorine?

Tick (✓) one box.

$Question 11, shown as an image$

[1]

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Chemistry Paper 9 June 2023 Higher tier, Question 3 1 mark

Which gas bleaches damp litmus paper?

A Carbon dioxide

B Chlorine

C Hydrogen

D Oxygen

$Question 3, shown as an image$

[1]

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Chemistry Paper 3 June 2022 Foundation tier, Question 2 1 mark

What is the test for oxygen gas?

A It goes ‘pop’ when lit.

B It relights a glowing splint.

C It turns damp red litmus paper blue.

D It turns limewater cloudy.

$Question 2, shown as an image$

[1]

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Chemistry Paper 9 June 2022 Higher tier, Question 14 18 marks

Calcium is a metal found in Group 2 of the Periodic Table.

(a)

Draw the arrangement of electrons in an atom of calcium.

[1]

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(b)

Calcium is a metal which can conduct electricity.

Describe the structure and bonding in a metal and explain why metals can conduct electricity.

You can include a diagram in your answer.

[4]

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(c)

Calcium reacts with water to form a solution of calcium hydroxide, Ca(OH)₂, and hydrogen.

(c)(i)

Write the balanced symbol equation for the reaction of calcium with water.

Include state symbols in your equation.

[3]

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(c)(ii)

A solution of calcium hydroxide is also called limewater.

Name the gas limewater is used as a test for.

[1]

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(d)

(d)(i)

Calculate the number of moles in 1.88 g of calcium hydroxide.

Give your answer to 2 significant figures.

Relative atomic mass (A_r): H = 1.0 O = 16.0 Ca = 40.1

[3]

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(d)(ii)

Use your answer to part (d)(i) to calculate the concentration of calcium hydroxide in the solution formed.

Give your answer in mol / dm³.

Concentration of solution =........ mol / dm³

[2]

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(e)

A student adds an excess of dilute hydrochloric acid, HC l, to a solution of calcium hydroxide, Ca(OH)₂.

(e)(i)

Write the balanced ionic equation for the reaction of dilute hydrochloric acid and a solution of calcium hydroxide.

[1]

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(e)(ii)

Describe and explain how the pH of the solution of calcium hydroxide changes as the dilute hydrochloric acid is added until it is in excess.

[3]

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Chemistry Paper 3 June 2019 Foundation tier, Question 3 1 mark

A student tests which gas is produced in a reaction using a glowing splint. The gas re-lights the glowing splint.

What is the name of the gas?

A Carbon dioxide

B Chlorine

C Hydrogen

D Oxygen

$Question 3, shown as an image$

[1]

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Chemistry Paper 4 June 2019 Foundation tier, Question 11 13 marks

This question is about Group 1 and Group 7 elements.

(a)

A Group 1 element D reacts with water.

This is the equation:

$Question 11, shown as an image$

(a)(i)

Name element D.

[1]

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(a)(ii)

A teacher shows this reaction to his class.

Describe one safety precaution he should use.

[1]

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(a)(iii)

E is a colourless gas.

How can you show if the gas is hydrogen or oxygen?

Describe the tests for hydrogen and oxygen, and the results you would expect with gas E.

test for hydrogen........

result with gas E........

[2]

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(a)(iv)

Group 1 elements are very reactive.

Write down the reason why.

[1]

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(b)

Table 11.1 shows the densities of the first four Group 1 elements at room temperature_.

(b)(i)

Calculate how many times larger the density of rubidium is than the density of lithium

Give your answer to 1 significant figure.

[2]

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(b)(ii)

1 g of sodium and 1 g of potassium are mixed to form an alloy.

Calculate the density of the alloy.

Density =........ g / cm³

[1]

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(b)(iii)

The element caesium (Cs) is also in Group 1. Caesium is found below rubidium in the Periodic Table.

Use the information in Table 11.1 and your knowledge of trends in properties for Group 1 elements to estimate the density of caesium.

Density of caesium =........ g / cm³

[1]

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(c)

A student reacts a solution of KBr with chlorine, Cl₂.

(c)(i)

Balance the equation for this reaction.

$Question 11, shown as an image$

[1]

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(c)(ii)

What is the name of the chemical KBr?

Tick (✓) one box.

$Question 11, shown as an image$

[1]

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(c)(iii)

What does the reaction tell you about the reactivity of Br₂ and Cl₂?

Explain your answer.

[2]

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Chemistry Paper 4 June 2025 Foundation tier, Question 16, also on the Higher paper Foundation Chemistry Paper 4 · June 2025 · Question 16 Also on Higher 12 marks

Chemistry Paper 9 June 2025 Higher tier, Question 15 Higher Chemistry Paper 9 · June 2025 · Question 15 13 marks

Chemistry Paper 10 June 2025 Higher tier, Question 11, also on the Foundation paper Higher Chemistry Paper 10 · June 2025 · Question 11 Also on Foundation 12 marks

Chemistry Paper 3 June 2024 Foundation tier, Question 3 Foundation Chemistry Paper 3 · June 2024 · Question 3 1 mark

Chemistry Paper 3 June 2023 Foundation tier, Question 11 Foundation Chemistry Paper 3 · June 2023 · Question 11 8 marks

Chemistry Paper 9 June 2023 Higher tier, Question 3 Higher Chemistry Paper 9 · June 2023 · Question 3 1 mark

Chemistry Paper 3 June 2022 Foundation tier, Question 2 Foundation Chemistry Paper 3 · June 2022 · Question 2 1 mark

Chemistry Paper 9 June 2022 Higher tier, Question 14 Higher Chemistry Paper 9 · June 2022 · Question 14 18 marks

Chemistry Paper 3 June 2019 Foundation tier, Question 3 Foundation Chemistry Paper 3 · June 2019 · Question 3 1 mark

Chemistry Paper 4 June 2019 Foundation tier, Question 11 Foundation Chemistry Paper 4 · June 2019 · Question 11 13 marks

Certified Combined Science memes. Peer-reviewed by nobody.

Chemistry Paper 4 June 2025 Foundation tier, Question 16, also on the Higher paper 12 marks

Chemistry Paper 9 June 2025 Higher tier, Question 15 13 marks

Chemistry Paper 10 June 2025 Higher tier, Question 11, also on the Foundation paper 12 marks

Chemistry Paper 3 June 2024 Foundation tier, Question 3 1 mark

Chemistry Paper 3 June 2023 Foundation tier, Question 11 8 marks

Chemistry Paper 9 June 2023 Higher tier, Question 3 1 mark

Chemistry Paper 3 June 2022 Foundation tier, Question 2 1 mark

Chemistry Paper 9 June 2022 Higher tier, Question 14 18 marks

Chemistry Paper 3 June 2019 Foundation tier, Question 3 1 mark

Chemistry Paper 4 June 2019 Foundation tier, Question 11 13 marks