OCR GCSE Combined Science A (Gateway) Chemistry Paper 10 Higher November 2020 question paper J250/10

What is an example of a biological catalyst?

A A lipid

B An amino acid

C An enzyme

D A substrate

The table shows the boiling points of the first five Group 0 elements.

Which statement describes the trend in the boiling points?

A The boiling points decrease as the molecules get larger.

B The boiling points decrease as the molecules get smaller.

C The boiling points increase as the atoms get larger.

D The boiling points increase as the atoms get smaller.

The table shows the melting and boiling points of bromine.

Which change of state happens when bromine is cooled from 65 °C to −5 °C?

A Condensation

B Evaporation

C Freezing

D Melting

The composition of the Earth’s atmosphere has changed over the last 4.5 billion years.

Which gas has increased by the largest amount?

A Ammonia

B Nitrogen

C Oxygen

D Water vapour

Copper can be extracted from copper sulfide by heating it in air.

Copper sulfide contains 74.0% copper by mass.

An ore contains 2.00% copper sulfide.

What is the maximum mass of copper that can be extracted from 150 kg of the ore?

A 1.48 kg

B 2.22 kg

C 3.00 kg

D 111 kg

Look at the reaction.

Which statement explains why the rate of reaction changes as the pressure increases?

A The energy of the particles increases.

B The particles collide with more force.

C The particles move faster.

D There are more particles in the same volume.

The rate of reaction of marble chips with dilute hydrochloric acid depends on the surface area of the marble chips.

Which surface area of the marble chips gives the highest rate of reaction?

0.673 mm² A

1030 mm² B

2.18 × 10³ mm² C

4.98 × 10⁻² mm² D

The Earth’s early atmosphere is thought to have contained large amounts of carbon dioxide.

Which process does not explain how the amount of carbon dioxide in the atmosphere was decreased?

A It became ‘locked up’ in fossil fuels.

B It dissolved in the oceans.

C It reacted to produce metal oxides found in metal ores.

D It was used in photosynthesis by green plants.

Look at the flowchart. It shows how crude oil is changed into useful substances.

Complete the flowchart with the name of Process 2.

Table 11.1 shows the supply and demand of two fractions of crude oil.

Explain the importance of Process 2.

Use information from Table 11.1 in your answer.

The hydrocarbon fractions from Process 1 contain different alkanes.

Table 11.2 shows the boiling point of different alkanes produced in Process 1.

Complete Table 11.2 with an estimate of the missing boiling point for an alkane molecule

with 3 carbon atoms.

Write the formula for an alkane with 7 carbon atoms.

A student investigates the rate of a reaction at different concentrations.

Fig. 12.1 shows the apparatus he uses.

The student adds dilute hydrochloric acid to the sodium thiosulfate solution. He times how long it takes for the cross to disappear. This is the reaction time.

The student repeats the experiment at different concentrations of sodium thiosulfate solution.

The concentration of hydrochloric acid is the same in each experiment.

He plots the results of the experiment on a graph, as shown in Fig. 12.2.

Look at the equation for the reaction.

Na₂S₂O₃(aq) + 2HCl (aq) → 2NaCl (aq) + H₂O(l) + S(s) + SO₂(g)

Which product in the reaction makes the cross disappear?

Tick (✓) one box.

The rate of reaction can be calculated using the equation:

Use the graph in Fig. 12.2 to calculate the rate of reaction when the concentration of sodium thiosulfate solution is 0.25 mol / dm³.

Give your answer to 2 decimal places.

Rate of reaction =........ / s

Describe the trend shown by the graph in Fig. 12.2.

State how the rate of reaction changes as the sodium thiosulfate concentration changes.

Another student investigates the effect of temperature on the rate of reaction.

She calculates the rate of reaction at different temperatures, as shown in the table.

Predict the rate of reaction at 70 °C.

Predicted rate of reaction =........ / s

Hydrogen peroxide solution decomposes slowly to form water and oxygen.

Look at the equation for the reaction.

2H₂O₂(aq) → 2H₂O(l) + O₂(g)

This reaction, shown in Fig. 13.1, is very slow.

Fig. 13.1

A student thinks that adding manganese(IV) oxide, MnO₂, will catalyse the decomposition reaction.

Her experiment is shown in Fig. 13.2.

When she puts the glowing spill into the test tube in Fig. 13.2 the spill relights.

The student separates the manganese(IV) oxide from the reaction mixture.

She adds this manganese(IV) oxide to a new solution of hydrogen peroxide.

Predict the results of this experiment if manganese(IV) oxide is a catalyst.

Explain your answer.

Table 14.1 shows the melting points of some of the Group 1 metals.

Plot the data in Table 14.1 on the grid in Fig. 14.1.

Draw a line of best fit.

Describe the relationship between the atomic number of the Group 1 metals and their melting points shown in Fig. 14.1.

Describe the metallic bonding in sodium.

Use information from Fig. 14.2 in your answer.

Look at the melting points of sodium and lithium in Table 14.1.

Suggest a reason for the difference in their melting points.

This question is about the Earth’s atmosphere and the greenhouse effect.

Scientists think that without the greenhouse effect the average temperature of the Earth’s surface would be about −18 °C.

Explain how the greenhouse effect keeps the average temperature above −18 °C.

Many scientists think that human activity is enhancing the greenhouse effect and leading to global warming.

Explain this statement.

Student A thinks that the increased use of electric cars would help reduce the greenhouse effect.

Student B thinks that the increased use of electric cars would not help reduce the greenhouse effect.

Explain why each student may be correct.

The waste gases from vehicle engines contain oxides of nitrogen.

Explain how the oxides of nitrogen are formed in an engine.

Most vehicles are fitted with catalytic converters. They reduce the amount of the oxides of nitrogen released into the atmosphere.

Describe why this is important.

16* Nitrogen and hydrogen react to form ammonia in a dynamic equilibrium.

The table shows the amount of ammonia formed at different temperatures and pressures.

Describe and explain how the percentage of ammonia formed changes with temperature and pressure.

Use the information provided in the table and your knowledge of reactions in dynamic equilibrium.

The alkanes in crude oil can be separated by fractional distillation.

This is because they have different boiling points.

The table shows the boiling points of hexane and octane.

Hexane molecules are smaller than octane molecules.

Explain the difference in the boiling points of hexane and octane.

A teacher checks the boiling point of hexane.

The diagram shows his experiment.

The teacher slowly heats up the water until hexane boils.

He records the temperature at the boiling point of hexane.

A student thinks that this method can be used to determine the boiling point of hexane but not the boiling point of octane.

Explain why the student is correct.

The diagram shows what happens when a small amount of potassium bromide solution, KBr, is added to a solution of chlorine, Cl₂.

Write the balanced symbol equation for the reaction between potassium bromide, KBr, and chlorine, Cl₂.

Write down the name of the chemical which makes the solution orange.

In this reaction is chlorine oxidised or reduced?

Explain your answer.

Explain why chlorine is more reactive than bromine.