Combined Science A (Gateway) · OCR J250 · Chemistry Paper 9 · Higher · June 2025
Which statement describes a pure substance?
A A mixture of substances which melts at a single temperature.
B A mixture of substances which melts over a range of temperatures.
C One substance which melts at a single temperature.
D One substance which melts over a range of temperatures.
[1]
Which row describes the nucleus of an atom?
| Charge | Mass | |
| A | positive | contains little of the mass of the atom |
| B | positive | contains most of the mass of the atom |
| C | negative | contains little of the mass of the atom |
| D | neutral | contains most of the mass of the atom |
[1]
Which substance is made from rings of carbon atoms?
A Carbon monoxide
B Copper carbonate
C Graphene
D Poly(ethene)
[1]
The diagram shows a chemical reaction.
During the reaction the mass on the balance decreases.
Which state symbol describes the product that causes the mass to decrease?
A aq
B g
C l
D s
[1]
Which statement about how Mendeleev arranged his version of the Periodic Table is incorrect
A He arranged elements in order of atomic number.
B He arranged elements with similar properties in groups.
C He left gaps for undiscovered elements.
D He swapped the order of pairs of some elements.
[1]
A student performs a chromatography experiment on a mixture of dyes.
The solvent moves 8.0 cm up the chromatography paper.
The Rf value for one dye is 0.60.
What distance does this dye move up the chromatography paper?
A 4.0 cm
B 4.8 cm
C 6.0 cm
D 7.2 cm
[1]
The particle model is used to describe changes of state.
Which statement about the particle model is correct ?
A It takes into account the forces between particles.
B It takes into account the size of the particles.
C It takes into account the space between the particles.
D It represents the particles as inelastic spheres.
[1]
How many grams of NaOH are found in 50 cm3 of a 4 g / dm3 solution of NaOH(aq)? 10
A 0.08 g
B 0.2 g
C 2 g
D 80 g
[1]
A student investigates the reaction of magnesium carbonate and dilute sulfuric acid.
The student wants to measure the pH of the dilute sulfuric acid.
Suggest the pH of dilute sulfuric acid.
[1]
Name an indicator that the student could use to measure the pH of dilute sulfuric acid.
State the colour of the indicator after it has been added to the dilute sulfuric acid.
Name of indicator........
[2]
Name a piece of equipment the student could use to measure the pH more accurately.
[1]
When magnesium carbonate reacts with dilute sulfuric acid, it forms a salt, water and carbon dioxide.
What is the name of the salt?
[1]
The student adds an excess of magnesium carbonate to dilute sulfuric acid until no more of it reacts.
magnesium carbonate(s) + sulfuric acid(aq) 
salt(aq) + water(l) + carbon dioxide(g)
Magnesium carbonate is a white powder that is insoluble in water.
A colourless solution of the salt is formed.
Describe two observations the student would see as the reaction is happening.
[2]
The student separates the salt from the solution formed at the end of the reaction.
Step 1: They remove the excess magnesium carbonate.
Step 2: They remove the water from the salt solution.
State the names of the separation techniques used in Step 1 and Step 2.
[2]
The student measures the mass of the salt obtained when different masses of magnesium carbonate are added to the same volume of dilute sulfuric acid.
The table shows their results.
| Mass of magnesium carbonate (g) | Mass of the salt (g) |
| 1.0 | 1.4 |
| 2.0 | 2.9 |
| 3.0 | 4.3 |
| 4.0 | 5.7 |
| 5.0 | 7.1 |
| 6.0 | 7.1 |
| 7.0 | 7.1 |
Describe the relationship between the mass of magnesium carbonate and the mass of the salt.
[2]
A student thinks that when 6.0 g of magnesium carbonate has been added it is in excess.
Explain why the student is correct.
[1]
Atoms are made from the sub-atomic particles protons, neutrons and electrons.
Table 12.1 shows the relative mass and relative charge of the three sub-atomic particles.
Complete Table 12.1 by writing the name of a sub-atomic particle in each space.
Table 12.1
| Sub-Atomic particle | Relative mass | Relative charge |
| ............................................. | 0.0005 | –1 |
| ............................................. | 1 | 0 |
| ............................................. | 1 | +1 |
[2]
An atom of phosphorus has an atomic number of 15 and a mass number of 31.
Calculate the number of protons, neutrons and electrons in this atom of phosphorus.
[2]
Phosphorus reacts with oxygen to form an oxide called phosphorus trioxide.
Phosphorus trioxide has the molecular formula P4O6.
What is the empirical formula of phosphorus trioxide?
Tick (✓) one box.
[1]
Complete the balanced symbol equation for the reaction of phosphorus trioxide with water.
[2]
Table 12.2 shows the melting point and boiling point of phosphorus trioxide.
Table 12.2
| Melting point (°C) | Boiling point (°C) |
| 24 | 173 |
In the box draw the particle arrangement for phosphorus trioxide at 100 °C.
[1]
The properties of materials depend on their structure and bonding.
The table shows some information about four materials.
Draw four lines to connect each material with its correct structure.
[4]
Ethene, C2H4, has this structure.
Complete the dot and cross diagram for a molecule of ethene.
Only show the outer shell electrons.
[2]
Explain why ethene has a low boiling point.
Use ideas about structure and bonding.
[2]
The equation shows how ethene can be produced.
The table shows some bond energies.
| Bond | Bond energy (kJ / mol) |
| C–C | 347 |
| C–H | 413 |
| C=C | 612 |
| H–H | 436 |
Calculate the total energy transferred to break all the bonds in the reactant.
Energy transferred to break all the bonds =........ kJ / mol
[1]
Calculate the total energy transferred to make all the bonds in the products.
Energy transferred when all the bonds are made =........ kJ / mol
[1]
Use your answers to parts (i) and (ii) to calculate the energy change for the reaction.
Energy change =........ kJ / mol
[1]
Sodium hydroxide, NaOH, and calcium hydroxide, Ca(OH)2, are ionic compounds that dissolve in water to form alkaline solutions.
Why are solutions of sodium hydroxide and calcium hydroxide called alkalis?
[1]
Explain why the formula of sodium hydroxide is NaOH but the formula of calcium hydroxide is Ca(OH)2.
[3]
The electrolysis of a sodium hydroxide solution produces hydrogen at the cathode rather than sodium.
Explain why.
[3]
When carbon dioxide is bubbled through a calcium hydroxide solution it turns cloudy white.
This is the equation for the reaction.
Which chemical in the equation turns the solution cloudy white?
[1]
What is the alternative name for the calcium hydroxide solution?
[1]
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 (Ar): H = 1.0 C = 12.0 O = 16.0 Ca = 40.1
[4]
The paper as printed
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