OCR GCSE Chemistry A (Gateway) Paper 3 Higher June 2025 question paper J248/03

1h 45m 90 marks

23 questions

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How many covalent bonds can a carbon atom form?

A 2

B 4

C 6

D 8

$Question 1, shown as an image$

[1]

Answer

What is the ionic equation for neutralisation?

$Question 2, shown as an image$

[1]

Answer

Which atomic model was developed by Thomson?

$Question 3, shown as an image$

[1]

Answer

The diagram shows calcium carbonate, CaCO₃, reacting with an acid.

The equation for the reaction is:

$Question 4, shown as an image$

What happens to the mass displayed on the balance as the reaction progresses?

A Decreases

B Decreases then increases

C Increases

D Stays the same

$Question 4, shown as an image$

[1]

Answer

Which ion do solutions of all alkalis contain?

A K +

B H +

C OH –

D SO₄^2–

$Question 5, shown as an image$

[1]

Answer

What is the relative formula mass of butanoic acid, C₃H₇COOH?

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

A 29.0

B 44.0

C 88.0

D 120.0

$Question 6, shown as an image$

[1]

Answer

What type of bonding is found in all polymers?

A Covalent

B Electrostatic

C Ionic

D Metallic

$Question 7, shown as an image$

[1]

Answer

Propene has the molecular formula C₃H₆.

What is the empirical formula?

A CH₂

B CH₃

C CH₂CHCH₃

D C₃H₆

$Question 8, shown as an image$

[1]

Answer

Which statement is true of all the diagrams of a water molecule?

A Shows all the atoms

B Shows all the electrons

C Shows the bonds between the atoms

D Shows the movement of the electrons

$Question 9, shown as an image$

[1]

Answer

Aluminium sulfate contains aluminium ions Al³⁺ and sulfate ions SO₄^2–.

What is the formula for aluminium sulfate?

A Al SO₄

B Al(SO₄)₂

C Al₂SO₄

D Al₂(SO₄)₃

$Question 10, shown as an image$

[1]

Answer

Where is beryllium found in the Periodic Table?

$Question 11, shown as an image$

[1]

Answer

Ethene reacts with bromine to form dibromoethane.

What is the energy change for the reaction?

Energy required to break bonds (kJ / mol)	Energy released from forming bonds (kJ / mol)
2453	2548

A – 48 kJ / mol

B –95 kJ / mol

C 95 kJ / mol

D 190 kJ / mol

$Question 12, shown as an image$

[1]

Answer

Which of the following reactions does not show a neutralisation reaction?

A Magnesium + hydrochloric acid $fraction$ magnesium chloride + hydrogen

B Magnesium carbonate + hydrochloric acid $fraction$ magnesium chloride + water + carbon dioxide

C Magnesium hydroxide + hydrochloric acid $fraction$ magnesium chloride + water

D Magnesium oxide + hydrochloric acid $fraction$ magnesium chloride + water

$Question 13, shown as an image$

[1]

Answer

Copper chloride solution is electrolysed.

What is the half equation for the reaction at the negative electrode (cathode) ?

$Question 14, shown as an image$

[1]

Answer

Which diagram shows the titration curve when a weak base is added to a strong acid ?

$Question 15, shown as an image$

[1]

Answer

Scientists are developing the use and application of nanoparticles.

(a)

The table shows the diameters of four different particles.

Particle	Diameter (nm)
A	97
B	2100
C	11
D	0.73

Which two particles are nanoparticles?

Explain your answer.

[2]

Answer

(b)

(b)(i)

One use of nanoparticles is in medicines.

State one other use of nanoparticles.

Explain why they can be used for that purpose.

Use........

Explanation........

[2]

Answer

(b)(ii)

Some scientists are worried about the risks of using nanoparticles.

Which statements are risks to humans of using nanoparticles?

Tick (✓) two boxes.

$Question 16, shown as an image$

[2]

Answer

(c)

A cube-shaped nanoparticle has sides of length 10 nm.

$Question 16, shown as an image$

Calculate the surface area to volume ratio of the cube.

Use the equation:

$Question 16, shown as an image$

[3]

Answer

This question is about separation techniques.

(a)

What is meant by a pure substance?

[1]

Answer

(b)

(b)(i)

A student does a chromatography experiment to separate some dyes.

The diagram shows how they set up their equipment.

The student’s experiment will not work to separate the dyes.

Suggest two changes the student can make so that the experiment will work.

[2]

Answer

(b)(ii)

The student calculates that a dye has an R_f value of 0.67.

The table shows the R_f value of different dyes.

Colour of dye	R_f value
Blue	0.15–0.20
Red	0.35–0.40
Pink	0.40–0.80
Yellow	0.75–0.80

Which dye did they use in their experiment?

Explain your answer.

Dye........

Explanation........

[2]

Answer

(c)

The diagram shows a chromatogram for another dye.

Calculate the R_f value of the dye.

$Question 17, shown as an image$

[2]

Answer

(d)

A student separates substance S from a mixture of substances S and T.

The starting mass of the mixture is 9.7 g and they obtain 5.1 g of pure substance S.

Calculate the mass of pure substance S that could be separated from 15.0 g of the mixture.

[2]

Answer

A group of students are investigating chemical reactions.

They add magnesium powder to copper sulfate solution.

They predict this will cause an increase in temperature, as they believe the reaction is exothermic.

(a)

The students collect the apparatus needed to test their theory.

Describe an experiment the students can do to measure the increase in temperature.

You can include a labelled diagram in your answer.

Optional diagram:

[4]

Answer

(b)

The students do the experiment five times.

The table shows the students’ results.

Experiment	Temperature increase (°C)
1	37
2	39
3	53
4	22
5	48

The students’ results show that their experiment is not repeatable.

Explain why.

[1]

Answer

(c)

The students draw a reaction profile for the reaction.

(c)(i)

Which part of the reaction profile shows the activation energy?

Tick (✓) one box.

$Question 18, shown as an image$

[1]

Answer

(c)(ii)

Which part of the reaction profile shows the energy change?

Tick (✓) one box.

$Question 18, shown as an image$

[1]

Answer

Atoms contain three subatomic particles: protons, neutrons and electrons.

(a)

The table shows some information about the subatomic particles.

Subatomic particle	Relative mass	Relative charge
Electron	...........................	...........................
Neutron	1	...........................
Proton	1	+1

Complete the table to show the relative mass and relative charge of each subatomic particle.

[3]

Answer

(b)

Describe how a lithium atom forms a lithium ion.

[1]

Answer

(c)

Lithium exists as two isotopes.

Complete the sentence about isotopes.

Use words from the list.

atom electrons element ion neutrons protons

Isotopes are atoms of the same........ with the same number of........

but different numbers of........

[3]

Answer

(d)

Lithium can bond with fluorine to form lithium fluoride.

Draw the dot and cross diagram to show the bonding in lithium fluoride.

You only need to show the outer shell electrons.

[2]

Answer

(e)

A sample of lithium is 11.5 cm wide.

Estimate how many lithium atoms would fit across the width of the sample.

Use your knowledge of the typical radius of atoms in your calculation.

[3]

Answer

20* This question is about structure and bonding.

The table shows some information about three different substances.

Substance	Melting point (°C)	Boiling point (°C)	Conducts electricity?
J	734	1435	yes, when molten or in solution
K	–182	–162	no
L	3422	5930	yes

It is also known that substance L is malleable.

Identify the type of structure and bonding in each substance.

Explain the properties shown in the table for each substance in terms of the type of structure and bonding.

[6]

Answer

This question is about allotropes of carbon.

(a)

Draw lines to connect each allotrope structure with its correct name.

[2]

Answer

(b)

Graphite is used to make electrodes because it conducts electricity and has a high melting point.

(b)(i)

Explain why graphite conducts electricity.

[2]

Answer

(b)(ii)

Explain why graphite has a high melting point.

Use ideas about structure and bonding in your answer.

[2]

Answer

A student reacts solid calcium carbonate, CaCO₃, with nitric acid, HNO₃.

Calcium nitrate, Ca(NO₃)₂, carbon dioxide and water are made.

Calcium nitrate is soluble in water.

(a)

Write the balanced symbol equation for the reaction.

Include state symbols.

[3]

Answer

(b)

(b)(i)

Plot the results on the graph.

[3]

Answer

(b)(ii)

Draw a curve of best fit.

[1]

Answer

(b)(iii)

Use the graph to estimate the volume of carbon dioxide that has been made after 30 seconds.

[1]

Answer

(c)

The student repeats the experiment with a different concentration of nitric acid.

Table 22.2 shows the results of both experiments.

Table 22.2

Time (s)	Volume of carbon dioxide (cm	³)
	Experiment 1	Experiment 2
0	0	0
10	15	21
20	31	39
30		41
40	45	47
50	47	47
60	47	47

Which experiment had the higher concentration of acid?

Explain your answer.

Experiment........

Explanation........

[2]

Answer

(d)

The diagram shows the apparatus the student uses.

Suggest another piece of equipment that could be used to measure the volume of carbon dioxide.

[1]

Answer

(e)

Calcium nitrate, Ca(NO₃)₂, can also be made in the reaction between calcium and nitric acid.

60 g of calcium reacts with excess nitric acid.

Calculate the mass of calcium nitrate made.

Relative atomic mass (A_r): Ca = 40.1 N = 14.0 O = 16.0

Give your answer to 3 significant figures.

[4]

Answer

(f)

[2]

Answer

Chromium is a shiny transition metal.

(a)

The equation shows the displacement reaction between aluminium and chromium oxide.

$Question 23, shown as an image$

Calculate the mass of chromium oxide needed to make 1 mol of chromium.

Relative atomic mass (A_r): Cr = 52.0 O = 16.0

[3]

Answer

(b)

Calculate the mass of one atom of chromium.

Relative atomic mass (A_r): Cr = 52.0

Avogadro constant = 6.02 × 10²³

[2]

Answer

(c)

Chromium is used for electroplating.

Chromium atoms lose electrons at the anode.

Chromium ions, Cr³⁺, gain electrons at the cathode.

Write balanced half equations to show the reactions at each electrode.

Anode........

Cathode........

[4]

Answer

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OCR J248 · Paper 3

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20

Question 21

Question 22

Question 23