OCR GCSE Combined Science A (Gateway) Chemistry Paper 10 Higher November 2021 question paper J250/10

A copper ore contains 66.4% copper. The ore is CuS.

What is the maximum mass of copper that can be extracted from 500 tonnes of the ore?

A 7.53 tonnes

B 66.4 tonnes

C 332 tonnes

D 33 200 tonnes

The diagram shows the percentage of greenhouse gases made from different sources.

The percentage of greenhouse gases produced from Residential is twice that produced from Agriculture.

What is the percentage of greenhouse gases produced from Residential?

A 9%

B 18%

C 27%

D 36%

An aqueous solution of sodium chloride, NaC l, is electrolysed using inert electrodes.

Which product is formed at the cathode?

A Chlorine

B Hydrogen

C Oxygen

D Sodium

The table shows some information about the Group 7 elements.

How many Group 7 elements are liquid at −40 °C?

A 0

B 1

C 2

D 3

Which row correctly shows a gas produced in a car engine and the problem it can cause?

The alkanes are members of a homologous series.

Which statement does not explain why alkanes are a homologous series?

A They are hydrocarbons.

B They have the same general formula.

C They react in similar ways.

D They show trends in physical properties.

The equation shows the reaction for the cracking of the alkane C₁₅H₃₂.

What is the formula of X ?

A C₃H₆

B C₃H₈

C C₅H₁₀

D C₅H₁₂

Silver, Ag, does not react with dilute hydrochloric acid, HC l.

Which statement is the correct explanation for this?

A Silver forms negative ions less easily than chlorine.

B Silver forms negative ions more easily than chlorine.

C Silver forms positive ions less easily than hydrogen.

D Silver forms positive ions more easily than hydrogen.

Look at the equations.

They show the two half equations that happen during the electrolysis of molten sodium chloride.

What is the correctly balanced equation for the electrolysis of molten sodium chloride?

The gradient of the tangent gives the rate of reaction. Use the tangent to calculate the rate of reaction at the start of the reaction.

Give your answer to 1 decimal place.

Rate of reaction =........ cm³ / minute

What happens to the rate of reaction as the reaction progresses?

Explain your answer using ideas about particles and collisions.

Another student repeats the experiment.

They increase the concentration of the dilute hydrochloric acid. They keep everything else in the experiment the same.

Does the gradient of the graph at the start of this student’s reaction decrease, increase or stay the same compared to the first student’s experiment?

Tick (✓) one box.

Give a reason for your answer.

Write down the volume of hydrogen gas that is produced at the end of this reaction.

A student investigates the reaction between zinc and dilute sulfuric acid.

The student observes that bubbles are produced slowly during the reaction.

They want to find a catalyst for the reaction. They repeat the experiment, but each time they add a small piece of a different metal, R, S and T.

Look at the student’s results.

State if the metals, R, S and T are catalysts or not.

Explain your answers using the information in the table and your knowledge of catalysts.

A teacher demonstrates the reactions of the Group 1 metals with water.

Table 13.1 shows information about how the first four elements in Group 1 react with water.

When potassium is added to cold water it melts and moves very quickly across the surface of the water.

Write down one other observation when potassium is added to cold water.

Complete Table 13.1 for rubidium.

Explain, in terms of electron loss or gain, the difference between lithium and sodium when they react with cold water.

Table 13.2 shows the density of the Group 1 metals from lithium to caesium.

Which Group 1 metal does not fit the general trend?

Explain your answer using information from Table 13.2.

Crude oil is a mixture of alkanes which can be separated into different fractions.

The different fractions have a range of different boiling points.

The diagram shows the process of fractional distillation.

Explain how fractional distillation separates the crude oil into fractions.

Icosane, C₂₀H₄₂, is an alkane found in one of the fractions.

It has a boiling point of 343 °C.

Which fraction, A, B, C, D, E or F, contains icosane?

Icosane is converted into more useful products by cracking.

State the two conditions used for cracking.

Many different products can form when cracking icosane.

In one reaction, a molecule of icosane (C₂₀H₄₂) forms a molecule of hydrogen, H₂, and one other product.

Write the balanced symbol equation for this reaction.

* Fraction A contains the alkanes methane, ethane, propane and butane.

Table 14.1 shows some information about these four alkanes.

Describe and explain the similarities and differences in the boiling point of these four alkanes.

Use information in Table 14.1 and your knowledge of structure and bonding in your answer.

Phytoextraction is a method of producing metals such as copper using plants which are harvested and burnt to produce an ash.

The ash is reacted with sulfuric acid to produce a solution of copper(II) sulfate.

Copper can be extracted by adding iron to the solution of copper(II) sulfate.

Explain why.

1 kg of plant ash can produce 2500 mg of copper.

Calculate the mass of ash (in kg) needed to produce 50 kg of copper.

1 kg = 1 × 10⁶ mg

Describe one advantage and one disadvantage of producing copper by phytoextraction.

Copper can be produced from a copper(II) sulfate solution by electrolysis.

A student investigates how the mass of copper produced changes with the size of the current used during the electrolysis. The student varies the current used during electrolysis and investigates the mass of copper produced at the cathode.

The diagram shows the apparatus they use.

Copper(II) sulfate solution

The student:

• Measures the mass of the dry cathode at the start of the experiment.

• Switches the power pack on for 10 minutes.

• Removes the cathode and washes it with water.

• Dries the cathode.

• Measures the mass of the cathode again.

• Calculates the mass of copper formed at the cathode.

The student repeats the experiment at different currents.

They plot a graph of their results.

The copper(II) sulfate solution contains copper ions, Cu²⁺. (a)

Write the balanced half equation for the formation of copper at the cathode.

Include state symbols in the equation.

Look at the graph.

The student decides that the result for the mass of copper formed at the cathode at 2 A is incorrect.

Give a reason for this result.

Has the student drawn the correct line of best fit?

Give a reason for your answer.

Explain how repeating the experiment could improve the accuracy of the results.

Use the graph to calculate the mass of copper produced by a current of 15 A.

Give your answer to 1 significant figure.

When a reversible reaction is left in a closed system, an equilibrium is reached.

Look at the equation.

It shows the equilibrium between NO₂(g) and N₂O₄(g).

Fig. 17.1 shows how the reaction rate of the forward and backward reactions change as the equilibrium is reached.

Describe how Fig. 17.1 shows that the equilibrium has been reached.

Fig. 17.2 shows how the concentrations of NO₂(g) and N₂O₄(g) change as the equilibrium is reached.

Describe how Fig. 17.2 shows that the equilibrium has been reached.

Each of the equations, A–E, shows a reversible reaction.

∆H shows the energy change of the forward reaction.

• If ∆ H is negative the forward reaction is exothermic.

• If ∆ H is positive the forward reaction is endothermic.

Write the letter, A – E, of one equation where more product is formed when the temperature is decreased.

Write the letter, A – E, of one equation where the amount of product is unchanged when the pressure is increased.

Write the letter, A – E, of one equation where more product is formed when either the temperature is increased or when the pressure is decreased.