OCR GCSE Chemistry A (Gateway) Paper 3 Higher June 2024 question paper J248/03

Which property is characteristic of a metal?

A It forms acidic oxides.

B It is brittle.

C It is malleable.

D It reacts with acid to form carbon dioxide gas.

Graphite and graphene are allotropes of carbon.

Which statement is correct about graphite and graphene?

A Graphite has delocalised electrons, graphene uses all electrons in bonding.

B Graphite has four bonds from each carbon atom, graphene only has three.

C Graphite is a giant covalent structure, graphene is not.

D Graphite is made up of layers, graphene is a single layer.

Which statement about a reducing agent is correct?

A It oxidises another species and is itself oxidised.

B It oxidises another species and is itself reduced.

C It reduces another species and is itself oxidised.

D It reduces another species and is itself reduced.

Which statement about alkalis is correct?

They form H + ions in solution. A

B They have a pH value greater than 7.

C They react with metals to form a salt and hydrogen.

D They turn universal indicator red.

Which equipment is needed to set up an electrolysis experiment?

A A battery, a beaker, a funnel and wires

B A battery, a beaker, electrodes and wires

C A battery, crocodile clips, electrodes and a thermometer

D A beaker, electrodes, a funnel and a thermometer

Which products are formed in the electrolysis of sodium chloride solution?

How did Mendeleev group elements together to develop his Periodic Table?

A Based on chemical properties and left gaps

B Based on mass number and atomic number

C Based on physical properties and atomic number

D Based on physical properties and left gaps

What is the mass of one atom of beryllium, Be?

Relative atomic mass (A_r): Be = 9.0.

The Avogadro constant is 6.02 10²³.

Zinc reacts with iron chloride to form zinc chloride and iron.

What is the balanced ionic equation for this reaction?

An element has the electronic configuration 2.8.4.

Which group and period is the element in?

A Group 2 as it has 2 electron shells. Period 4 as it has 4 electrons in the outer shell.

B Group 2 as it has 2 electrons in the outer shell. Period 4 as it has 4 electron shells.

C Group 4 as it has 4 electron shells. Period 3 as it has 3 electrons in the outer shell.

D Group 4 as it has 4 electrons in the outer shell. Period 3 as it has 3 electron shells.

Copper nitrate decomposes into copper oxide, nitrogen dioxide and oxygen.

How many moles of products are formed if 18 mol of copper nitrate decomposes?

Solutions can have different pH values.

Which two solutions have concentrations of H + ions that differ by a factor of 100?

A pH 1 and pH 2

B pH 1 and pH 4

C pH 2 and pH 4

D pH 3 and pH 6

At 25 °C, fluorine is a gas, bromine is a liquid and iodine is a solid.

Which statement is correct?

A At 25 °C, bromine does not have enough heat energy to melt.

B At 25 °C, fluorine does not have enough heat energy to condense.

C Bromine has a higher boiling point than fluorine and a higher melting point than iodine.

D Iodine has a higher boiling point than bromine and a higher melting point than fluorine.

Calculate the surface area to volume ratio of tablet C.

Complete the sentence to describe the relationship between the surface area to volume ratio and the time taken to dissolve.

As the surface area to volume ratio........,

the tablet will take........ time to dissolve.

The scientist performs thin layer chromatography on solutions of each of the tablets.

The spots on the chromatogram are colourless.

State what the scientist could use to see the spots.

After the scientist uses a method to see the spots, the chromatogram for Tablet A is shown.

Calculate the R_f value for the spot seen from tablet A.

A student wants to separate a mixture of compounds.

Different separation methods are used depending on the mixture.

Draw lines to connect each separation method to the correct mixture.

The student decides to use simple distillation to separate a mixture.

They set up the apparatus shown in the diagram.

A liquid in the mixture is flammable.

Suggest a change the student could make to the apparatus to make the distillation safer.

The student wants to record the boiling point of the pure liquid that is collected in the collection flask.

Suggest an improvement the student could make to the apparatus so that they can record the boiling point.

The pure liquid collected has the molecular formula (C₂H₅)₂O and a boiling point of 35 °C.

Which statements about the pure liquid are correct ?

Tick (✓) two boxes.

Calculate the relative formula mass of a (C₂H₅)₂O molecule.

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

A scientist is studying two chemical reactions.

One reaction is exothermic, and one reaction is endothermic.

The reaction profile for the exothermic reaction is shown.

Explain how you can tell the reaction profile is for an exothermic reaction.

Describe one difference and one similarity the scientist will see in the reaction profile for the endothermic reaction.

Difference........

Similarity........

Calculate the energy transferred when all the bonds form in the products.

Energy transferred =........ kJ / mol

The energy transferred when all the bonds break in the reactants is 6480 kJ / mol.

Use your answer to part (b)(i) to calculate the energy change for this reaction.

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

A student studies a different reaction.

They want to find out if it is exothermic or endothermic.

Some possible steps for a method are given in the list.

Write five steps from the list in the correct order to describe the method the student should use.

A Add the solid to the solution.

B Cover the top of the reaction with a lid.

C Cover the top of the reaction with cotton wool.

D Put on safety goggles.

E Put the solution into a beaker and use a thermometer to record the temperature before the reaction starts.

F Put the solution into a polystyrene cup and use a thermometer to record the temperature before the reaction starts.

G Use a thermometer to record the temperature as the reaction progresses.

Step 1 Step 2 Step 3 Step 4 Step 5

The student plots their results on a graph.

The student concludes that the reaction is exothermic.

Explain why the student is correct.

Many scientists were involved in the development of the atomic model.

Describe two ways Rutherford’s atomic model was an improvement on Thomson’s “plum pudding” atomic model.

Atoms are either oxidised or reduced to form ions.

Complete the sentences about how atoms form ions.

Atoms are........ to form positive ions. Atoms........

electrons to form positive ions.

Atoms are........ to form negative ions. Atoms........

electrons to form negative ions.

The table shows information about three different ions.

Complete the table.

The element lithium exists as isotopes.

State one difference and one similarity between the Li + ions formed from different isotopes of lithium.

Difference........

Similarity........

A sample of magnesium metal is 5.2 cm wide.

Estimate how many Mg²⁺ ions would fit across the width of the sample of magnesium metal.

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

Ions are also formed when acids and alkalis dissolve in water.

Which statements about acid solutions are correct ?

Tick (✓) two boxes.

A student makes an acid solution with a pH of 3.

Describe two things the student could do to make a solution with a lower pH.

The particle model can be used to show changes of state.

Complete the diagram to show what happens to the particles as a solid changes to a liquid.

Which statements about changes of state are correct ?

Tick (✓) two boxes.

The amount of energy needed to melt a substance depends on the strength of the forces between particles.

The particle model has limitations when showing changes of state.

Explain two limitations of the particle model.

A scientist needs to choose a solid formulation that will be used at high temperatures.

The graphs show how the temperature changes as three different formulations, A, B and C, are

Which formulation should the scientist choose?

Explain your answer.

Formulation........

Explanation........

* The structures of diamond, chlorine, Cl₂, and poly(ethene) are shown.

All the substances contain covalent bonds between the atoms.

Explain which substance has the highest melting point.

Use your knowledge of structure and bonding.

Magnesium chloride is an ionic compound.

Explain why ionic compounds can conduct electricity when dissolved in water, but not when solid.

Construct the dot and cross diagram for the ions in magnesium chloride, MgCl₂.

Show the outer electron shells only.

Dot and cross diagram:

Which method should the student use to make their sample?

Explain your answer.

Method........

Reason........

A teacher shows the student how to purify magnesium carbonate.

If the student knows how to purify magnesium carbonate, should they use the same method as they used in part (a) ?

Explain your answer.

The student reacts the magnesium carbonate they have made with hydrochloric acid.

Complete the balanced equation.

Include state symbols.

The student uses 0.2 mol of hydrochloric acid in the reaction. The hydrochloric acid is the limiting reagent.

At the end of the reaction, 0.82 g of magnesium carbonate is left unreacted.

Calculate the mass of magnesium carbonate that the student uses in the reaction.

Relative atomic mass (A_r): C = 12.0 Mg = 24.3 O = 16.0