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OCR GCSE Combined Science

Topic questions Energy changes Reaction profiles

Reaction profiles

10 questions · 71 marks · about 1.5 hours

Reaction profiles questions

TopicReaction profiles

OCR J250 Reaction profiles 10 questions

Chemistry Paper 3 June 2025 Foundation tier, Question 12 5 marks

A student investigates some exothermic and endothermic reactions.

They measure the temperature change in two reactions.

The table shows their results.

ReactionStart temperature (°C)End temperature (°C)Temperature change (°C)
1................12–4
21839+21
(a)

Complete the table by writing in the start temperature for Reaction 1.

[1]
Reveal mark scheme Mark scheme for question 12(a)
(b)

State and explain which reaction is exothermic and which is endothermic.

[2]
Reveal mark scheme Mark scheme for question 12(b)
(c)

The diagram shows a reaction profile for an exothermic reaction.

Figure for question 12
Question 12, shown as an image
(c)(i)

Which energy change, A, B or C, is the activation energy?

[1]
Reveal mark scheme Mark scheme for question 12(c)(i)
(c)(ii)

Which energy change, A, B or C, is the energy change for the reaction?

[1]
Reveal mark scheme Mark scheme for question 12(c)(ii)

Chemistry Paper 9 June 2024 Higher tier, Question 9 1 mark

Magnesium reacts very slowly with oxygen at room temperature.

When magnesium is heated in a Bunsen burner flame it burns very brightly after only a few seconds.

Which statement is correct?

A The activation energy for the reaction is high.

B The reaction is endothermic.

C Magnesium is an unreactive metal.

D Magnesium only reacts at very high temperatures.

Question 9, shown as an image
[1]
Reveal mark scheme Mark scheme for question 9

Chemistry Paper 3 June 2023 Foundation tier, Question 14 14 marks

Zinc, Zn, reacts with sulfuric acid, H2SO4, to form the salt, ZnSO4, and hydrogen.

(a)

Write the balanced symbol equation for the reaction of zinc with sulfuric acid.

[1]
Reveal mark scheme Mark scheme for question 14(a)
(b)

Name the salt, ZnSO4, made from zinc and sulfuric acid.

[1]
Reveal mark scheme Mark scheme for question 14(b)
(c)

To make sure all the sulfuric acid reacts, an excess of zinc is used.

Describe how universal indicator could be used to show that all the sulfuric acid has reacted.

[2]
Reveal mark scheme Mark scheme for question 14(c)
(d)(i)

Calculate the relative formula mass of ZnSO4.

Relative atomic mass (Ar): O = 16.0 S = 32.1 Zn = 65.4

Relative formula mass of ZnSO4 =........

[1]
Reveal mark scheme Mark scheme for question 14(d)(i)
(d)(ii)

The percentage mass of an element in a compound can be calculated using the formula

Question 14, shown as an image

Calculate the percentage mass of zinc in ZnSO4.

Give your answer to 1 decimal place.

[3]
Reveal mark scheme Mark scheme for question 14(d)(ii)
(e)

The reaction between zinc and sulfuric acid is exothermic.

(e)(i)

Explain what is meant by an exothermic reaction.

[1]
Reveal mark scheme Mark scheme for question 14(e)(i)
(e)(ii)

The diagram shows the reaction profile for the reaction.

Figure for question 14

Label the activation energy on the diagram.

[1]
Reveal mark scheme Mark scheme for question 14(e)(ii)
(e)(iii)

Explain the term activation energy.

[1]
Reveal mark scheme Mark scheme for question 14(e)(iii)
(f)

The table shows the temperature changes in four reactions.

The reaction between zinc and sulfuric acid is slightly exothermic.

Which shows the reaction between zinc and dilute sulfuric acid?

Give a reason for your answer.

ReactionStart temperature (°C)End temperature (°C)
A2019
B2064
C2022
D2020
[3]
Reveal mark scheme Mark scheme for question 14(f)

Chemistry Paper 9 June 2023 Higher tier, Question 16 6 marks

Figure for question 16
(a)(i)

Calculate the total energy transferred to break all the bonds in the reactants.

Energy transferred to break all the bonds =........ kJ / mol

[1]
Reveal mark scheme Mark scheme for question 16(a)(i)
(a)(ii)

Calculate the total energy transferred when all the bonds in the products are made.

Energy transferred when all the bonds are made =........ kJ / mol

[1]
Reveal mark scheme Mark scheme for question 16(a)(ii)
(a)(iii)

Use your answers to parts (i) and (ii) to calculate the energy change for the reaction.

Energy change =........ kJ / mol

[1]
Reveal mark scheme Mark scheme for question 16(a)(iii)
(b)
Figure for question 16
[3]
Reveal mark scheme Mark scheme for question 16(b)

Chemistry Paper 3 June 2022 Foundation tier, Question 7 1 mark

The diagram shows the reaction profile for a reaction.

Figure for question 7

Which row represents the activation energy and the energy change for the reaction?

Activation energyEnergy change
AXY
BXZ
CZX
DZY
Question 7, shown as an image
[1]
Reveal mark scheme Mark scheme for question 7

Chemistry Paper 9 November 2021 Higher tier, Question 15 10 marks

Carbon dioxide, CO2, is a covalently bonded molecule.

(a)

Explain what is meant by a covalent bond.

[2]
Reveal mark scheme Mark scheme for question 15(a)
(b)

Look at the diagram. It shows the structure of carbon dioxide.

Question 15, shown as an image

Complete the dot and cross diagram for carbon dioxide.

Figure for question 15
[2]
Reveal mark scheme Mark scheme for question 15(b)
(c)

The equation shows the formation of 1 mole of carbon dioxide from carbon monoxide and oxygen.

Question 15, shown as an image

The table shows the bond energies of some bonds.

BondBond energy (kJ / mol)
C≡O1070
O=O496
C=O743

Calculate the energy change for the formation of 1 mole of carbon dioxide.

Energy change =........ kJ / mol

[3]
Reveal mark scheme Mark scheme for question 15(c)
(d)(i)

Explain the term activation energy.

[2]
Reveal mark scheme Mark scheme for question 15(d)(i)
(d)(ii)

Look at your calculation in (c).

Suggest a value for the activation energy for the formation of 1 mole of carbon dioxide in this reaction.

[1]
Reveal mark scheme Mark scheme for question 15(d)(ii)

Chemistry Paper 9 November 2020 Higher tier, Question 13 4 marks

Hydrogen, H2, and chlorine, Cl2, react to make hydrogen chloride, HCl.

Question 13, shown as an image

The reaction is exothermic.

(a)

Look at Fig. 13.1. It shows the reaction profile for the reaction.

Figure for question 13

Complete Fig. 13.1 by filling in the two boxes.

Use the balanced symbol equation to help you.

[2]
Reveal mark scheme Mark scheme for question 13(a)
(b)
Figure for question 13
[2]
Reveal mark scheme Mark scheme for question 13(b)

Chemistry Paper 3 June 2019 Foundation tier, Question 16, also on the Higher paper 12 marks

A student investigates three reactions.

She wants to find out if the reactions are exothermic or endothermic.

Look at her results.

ReactionStart temperature (°C)Final temperature (°C)
X2125
Y2018
Z2224
(a)

Which reaction, X, Y or Z, is endothermic ?........

Explain your answer.

[2]
Reveal mark scheme Mark scheme for question 16(a)
(b)

Draw a labelled reaction profile for an endothermic reaction.

Use the following labels on your reaction profile:

• products

• energy change

• activation energy.

Figure for question 16
[4]
Reveal mark scheme Mark scheme for question 16(b)
(c)

Another student repeats the same reactions.

The student does the experiment in a polystyrene cup instead of a beaker.

Explain why using a polystyrene cup is an improvement to the method.

[2]
Reveal mark scheme Mark scheme for question 16(c)
(d)

The reaction between iron oxide and aluminium is very exothermic.

Look at the equation for the reaction.

Question 16, shown as an image
(d)(i)

During this reaction the aluminium is oxidised.

Explain what is meant by the term oxidised.

[1]
Reveal mark scheme Mark scheme for question 16(d)(i)
(d)(ii)

Pure iron metal is produced in the reaction.

Draw a diagram to show the bonding in a metal.

Label your diagram clearly.

[3]
Reveal mark scheme Mark scheme for question 16(d)(ii)

Chemistry Paper 9 June 2019 Higher tier, Question 11, also on the Foundation paper 12 marks

A student investigates three reactions.

She wants to find out if the reactions are exothermic or endothermic.

Look at her results.

ReactionStart temperature (°C)Final temperature (°C)
X2125
Y2018
Z2224
(a)

Which reaction, X, Y or Z, is endothermic ?........

Explain your answer.

[2]
Reveal mark scheme Mark scheme for question 11(a)
(b)

Draw a labelled reaction profile for an endothermic reaction.

Use the following labels on your reaction profile:

• products

• energy change

• activation energy.

Figure for question 11
[4]
Reveal mark scheme Mark scheme for question 11(b)
(c)

Another student repeats the same reactions.

The student does the experiment in a polystyrene cup instead of a beaker.

Explain why using a polystyrene cup is an improvement to the method.

[2]
Reveal mark scheme Mark scheme for question 11(c)
(d)

The reaction between iron oxide and aluminium is very exothermic.

Look at the equation for the reaction.

Question 11, shown as an image
(d)(i)

During this reaction the aluminium is oxidised.

Explain what is meant by the term oxidised.

[1]
Reveal mark scheme Mark scheme for question 11(d)(i)
(d)(ii)

Pure iron metal is produced in the reaction.

Draw a diagram to show the bonding in a metal.

Label your diagram clearly.

[3]
Reveal mark scheme Mark scheme for question 11(d)(ii)

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