OCR GCSE Combined Science A (Gateway) Chemistry Paper 10 Higher June 2023 question paper J250/10

Which reactions can be catalysed by an enzyme?

A Combustion reactions

B Electrolysis of metal ores

C Reactions in biological systems

D Reactions of metals with acids

Which row correctly describes the Group 0 elements?

A small piece of a Group 1 metal is added to a trough of water.

The metal floats, fizzes vigorously and melts to form a silvery ball.

Which Group 1 metal was added to the water?

A Lithium

B Potassium

C Rubidium

D Sodium

The equation shows a reaction of decane, C₁₀H₂₂, when it is heated with a catalyst.

C₁₀H₂₂ → C₅H₁₂ + C₃H₆ + C₂H₄

What is the name of this process?

A Cracking

B Displacement

C Electrolysis

D Reduction

The diagram shows the fractional distillation of crude oil.

Gases

Which row in the table describes the Gases fraction?

What is the percentage change in sulfur dioxide emissions from 1970 to 2010?

Iron, Fe, can be extracted from iron oxide, Fe₂O₃, in a blast furnace, by the reaction shown in the equation.

Fe₂O₃ + 3X → 2Fe + 3Y

What are the formulae of X and Y ?

When a solution of bromine, Br₂(aq), is mixed with a solution of sodium chloride, NaCl (aq), there is no reaction.

Why is there no reaction?

A Bromine gains electrons more easily than chlorine.

B Bromine loses protons more easily than chlorine.

C Chlorine gains electrons more easily than bromine.

D Chlorine loses protons more easily than bromine.

Which Group 7 element is most often added to tap water to make it potable?

A Bromine

B Chlorine

C Fluorine

D Iodine

When marble chips react with dilute hydrochloric acid, the mass of the reactants decreases.

The graph shows the loss in mass of the reactants with time.

What is the correct formula used to calculate the mean rate of reaction between 2 and 4 minutes?

The student has difficulty filling the measuring cylinder with water.

They change the measuring cylinder for a different piece of apparatus which allows them to measure the volume of hydrogen more accurately.

Name the piece of apparatus they use and complete the diagram below to show this apparatus.

Name of piece of apparatus........

Complete the balanced symbol equation for the reaction.

The student repeats the experiment. The only difference is they use a higher concentration of acid.

Draw a line on the graph to show the results of this experiment.

If the experiment is repeated at a higher temperature, the rate of reaction increases.

Explain why. Use ideas about particles and collisions.

The Earth’s early atmosphere was mainly water vapour and carbon dioxide.

The Earth’s atmosphere today is mainly nitrogen and oxygen with small amounts of other gases including carbon dioxide.

Complete the bar chart to show the percentage of nitrogen and oxygen found in the Earth’s

atmosphere today.

Explain how the amounts of water vapour and carbon dioxide in the Earth’s early atmosphere decreased over time.

Water vapour........

Carbon dioxide........

Explain how the amount of oxygen in the Earth’s atmosphere has increased over time.

The Earth’s early atmosphere may have trapped more of the sun’s heat than Earth’s atmosphere traps today.

Give a reason why.

The amount of carbon dioxide in the Earth’s atmosphere is 409.8 parts per million.

1 part per million is equal to 0.0001%

Calculate the percentage of carbon dioxide in the Earth’s atmosphere today.

Give your answer to 3 decimal places.

Copper can be extracted from its compounds by different processes.

Process 1

• Copper is extracted from copper oxide, CuO.

• The copper is extracted by heating copper oxide with carbon.

This is the equation for the reaction in Process 1.

2CuO(s) + C(s) → 2Cu(s) + CO₂(g)

Explain why carbon can be used to extract copper from copper oxide.

One of the products of this reaction causes an environmental problem.

Identify the product and describe its impact on the environment.

Process 2

• Copper is extracted from copper sulfide, CuS.

• Solid copper sulfide is broken down by bacteria to form a solution of copper sulfate, CuSO₄.

• The copper is extracted from the solution of copper sulfate by either reacting it with iron or by electrolysis.

Why is process 2 described as a biological method of metal extraction?

Describe two advantages of extracting copper from the solution of copper sulfate by reacting it with iron rather than using electrolysis.

Ores are rocks that contain metals or their compounds.

The table shows some information about high-grade and low-grade ores.

Explain the difference in the mass of metal contained in a high-grade and low-grade ore.

Use information from the table.

14* Magnesium, calcium and strontium are metals in Group 2 of the Periodic Table.

Tables 14.1 and 14.2 show some information about these metals.

Table 14.1

Reactions of the metals with cold water

Table 14.2

Energy required to form a 2+ ion

Barium is below strontium in Group 2.

Describe and explain the reactivity of barium.

Include observations of the reaction of barium with water.

Use information from Tables 14.1 and 14.2.

Iodine is an element in Group 7 of the Periodic Table.

Seaweed has small amounts of compounds containing iodine. It is possible to extract iodine from seaweed.

The diagram shows the stages in the extraction of iodine.

In Stage 1 iodide ions are produced by reduction.

Explain reduction in terms of electrons.

In Stage 2 iodide ions are oxidised to iodine.

Complete the half-equation for the oxidation of iodide ions into iodine.

In Stage 3 if the solution is heated for too long, iodine vapour is formed.

What colour is iodine vapour?

0.13 g of iodine is produced from 5.0 g of seaweed.

Calculate the percentage mass of iodine in the seaweed.

When a solution of yellow Fe³⁺(aq) ions is mixed with a solution of colourless SCN^–(aq) ions they 16 react to form a solution of red FeSCN²⁺(aq) ions.

This is an example of a dynamic equilibrium.

Complete the equation for this reaction.

Plot the results from the table on the graph. Two points have already been plotted for

you.

Draw a line of best fit.

What is the time it takes for the reaction to reach equilibrium?

Give a reason for your answer.

Time to reach equilibrium =........ seconds

A student increases the concentration of SCN – (aq) ions in the mixture. (c)

The mixture turns darker red.

Use Le Chatelier’s principle to explain the change in colour.

The student thinks that the forward reaction shown in (a) for the equilibrium is exothermic

Describe what the student should do to the equilibrium mixture to show that the forward reaction is exothermic.

Predict the student’s observations.