OCR GCSE Chemistry B (21st Century) Paper 3 June 2018 question paper

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Calcium carbonate reacts with excess hydrochloric acid to make carbon dioxide.

Here is the apparatus Jack uses to investigate the reaction.

Jack records the volume of carbon dioxide made every 200 seconds.

Here is a graph of his results.

(a)

Use the graph to calculate the rate of reaction over the first 100 s.

Rate =........ cm³ / s

[2]

Answer

(b)

Amaya wants to repeat Jack’s experiment.

She uses the same mass of calcium carbonate.

She uses the same volume and concentration of hydrochloric acid.

Which two other factors does she need to keep the same?

[2]

Answer

(c)

Jack repeats his experiment with more concentrated hydrochloric acid.

He keeps all other factors the same. The rate of reaction is faster.

Explain why.

Write about particles in your answer.

[2]

Answer

(d)

0.10 g of calcium carbonate makes 24 cm³ of carbon dioxide. (d)

Jack uses 0.070 g of calcium carbonate.

What volume of carbon dioxide does he make?

Give your answer to 2 significant figures.

[3]

Answer

Fizzy water can be found naturally.

The water is fizzy because it contains dissolved carbon dioxide gas. The carbon dioxide comes from the decomposition of rocks that contain carbonate compounds.

One compound found in rocks is magnesium carbonate.

Ali investigates the decomposition of magnesium carbonate by heating a small amount in a test tube. This is the equation for the reaction.

$Question 2, shown as an image$

(a)

Ali weighs the test tube before and after heating.

The mass of the test tube after heating is less.

Ali says that this means the law of conservation of mass is not correct.

Explain why Ali is wrong.

[2]

Answer

(b)

Calculate the atom economy for the production of carbon dioxide in this reaction.

$Question 2, shown as an image$

Give your answer to 1 decimal place.

[4]

Answer

(c)

In theory, 42.0 g of MgCO₃ loses 22.0 g of carbon dioxide when it completely decomposes.

Ali heats 4.2 g of MgCO₃.

(c)(i)

Calculate the mass of carbon dioxide lost when 4.2 g of MgCO₃ completely decomposes.

[1]

Answer

(c)(ii)

In Ali’s experiment, the mass of carbon dioxide lost is 1.8 g.

Calculate the percentage yield of carbon dioxide in Ali’s experiment.

[1]

Answer

(d)

Magnesium oxide, MgO, is an ionic compound.

Draw a ‘dot and cross’ diagram for the ions in magnesium oxide.

Show the outer electron shells only.

[2]

Answer

The table shows the properties of three polymers.

(a)

A firm wants to make cups to hold boiling water.

Discuss the suitability of each polymer.

[3]

Answer

(b)

Which of polymers A, B and C, has the weakest intermolecular forces?

Give a reason for your answer.

Polymer........

Reason........

[2]

Answer

(c)

Polymer A is an addition polymer.

Draw the structure of the monomer that forms polymer A.

[1]

Answer

The percentage of oxygen gas in the Earth’s atmosphere has generally increased over time.

This graph shows the percentage oxygen concentration in the Earth’s atmosphere over the last 4 billion years.

(a)(i)

Describe how the oxygen content of the Earth’s atmosphere has changed during the last four billion years.

[2]

Answer

(a)(ii)

The concentration of oxygen has increased from two billion years ago to today.

By what factor has it increased?

[1]

Answer

(a)(iii)

Explain what caused the sudden increase in oxygen concentration 2.5 billion years ago and explain why the concentration did not continue to rise.

[2]

Answer

(b)

Iron pyrites in rocks was oxidised to compounds like iron(III) sulfate by the oxygen in the early atmosphere.

Complete the balanced chemical equation for this reaction.

$Question 4, shown as an image$

[1]

Answer

Ling carries out an investigation of the halogens.

(a)

Ling reacts some chlorine solution with a solution of potassium bromide.

The solution turns brown.

Explain why.

Include an ionic equation in your answer.

[3]

Answer

(b)

Ling sees that the element astatine, At, is below iodine in Group 7.

She makes some predictions about astatine.

Which predictions about astatine are correct?

Tick (✓) two boxes.

$Question 5, shown as an image$

[1]

Answer

Nanoparticles of cerium oxide, CeO₂, are added to diesel fuel.

They act as a catalyst for the combustion of the fuel.

(a)

Describe a property of nanoparticles that makes them good catalysts.

[1]

Answer

(b)

The addition of nanoparticles allows more complete combustion of the fuel.

Kai talks about nanoparticles in diesel fuel.

Evaluate Kai’s statement.

In your answer give arguments for and against the use of nanoparticles.

[3]

Answer

(c)

[1]

Answer

(d)

A nanoparticle has a volume of 8 × 10^–27 m. (d)

A molecule has a volume of 4 × 10^–30 m.

Estimate how many moles of this molecule there are in the nanoparticle.

[3]

Answer

This is an equation for a reaction that occurs in a lightning flash.

$Question 7, shown as an image$

Very high temperatures are needed.

(a)(i)

Explain how you can tell that this equation refers to an equilibrium.

[1]

Answer

(a)(ii)

Use ideas about rates to explain what is happening when the reaction reaches dynamic equilibrium.

[2]

Answer

(b)

Scientists can use this reaction to make nitrogen compounds from gases in the air.

(b)(i)

Suggest a use for these compounds.

[1]

Answer

(b)(ii)

The scientists discuss increasing the pressure on the reaction.

Describe and explain the effect on the equilibrium position.

[2]

Answer

(c)

There are several ways of making nitrogen compounds from nitrogen gas in industry.

Give two reasons why scientists may choose this reaction and one against.

Reason for........

Reason against........

[3]

Answer

Manganese is a metallic element.

(a)

Manganese is made by heating manganese oxide, MnO₂, with carbon.

Carbon monoxide is also formed.

(a)(i)

Write a balanced chemical equation for this reaction.

Include state symbols in your equation.

[2]

Answer

(a)(ii)

Explain why carbon can be used to extract manganese from its compounds.

Use ideas about reactivity and reduction in your answer.

[2]

Answer

(b)

Explain how the atoms are held together in a metal.

Refer to this diagram in your answer.

[3]

Answer

Jane has a sample of a white powder, compound A.

(a)

Jane carries out a flame test on compound A and sees a lilac flame.

What can Jane conclude about compound A ?

[1]

Answer

(b)

Jane looks at the emission spectrum of compound A.

(b)(i)

Describe what an emission spectrum looks like.

[2]

Answer

(b)(ii)

Describe how Jane could use the spectrum to confirm her answer to (a).

[1]

Answer

(c)

Jane has a solution of compound B, sodium sulfate, Na₂SO₄.

She adds acidified barium chloride solution, BaCl₂, to a solution of compound B.

(c)(i)

What does she see when she does this?

[1]

Answer

(c)(ii)

Write a balanced chemical equation for the reaction that occurs.

[2]

Answer

Hydrogen for use as a fuel can be made by the electrolysis of water.

(a)

Which statements about the electrolysis of water are correct?

Ticks (✓) two boxes.

$Question 10, shown as an image$

[1]

Answer

(b)

This is an equation for the overall reaction that happens when water is electrolysed.

$Question 10, shown as an image$

Bond	Energy change (kJ / mol)
H–H	434
O=O	498
O–H	464

Use data in the table to calculate the energy needed to break and make bonds during the reaction.

Use your answers to calculate the energy change of the reaction.

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

[3]

Answer

(c)

Complete the reaction profile for the electrolysis of water.

Use these words to label the reaction profile.

hydrogen oxygen water activation energy

[3]

Answer

Aluminium is made by the electrolysis of molten aluminium oxide.

(a)

The ions present in molten aluminium oxide are Al³⁺ and O^2–. (a)

Write half-equations for the formation of aluminium and oxygen in the electrolysis cell.

Formation of aluminium........

Formation of oxygen........

[2]

Answer

(b)

Aluminium oxide does not conduct electricity when it is solid.

It conducts electricity when it is molten.

Explain why.

[3]

Answer

(c)

This is an equation for the overall reaction in the electrolysis cell.

$Question 11, shown as an image$

1.0 kg of aluminium is made in the cell.

Calculate the volume of oxygen (in dm³ at room temperature and pressure) that is made.

Assume one mole of gas has a volume of 24 dm³ at room temperature and pressure.

[4]

Answer

Sulfuric acid is used in car batteries. Mia has a sample of car battery acid that is diluted to $fraction$ of its original concentration.

She measures the concentration of this acid by titration.

(a)

This equation shows what happens when pure sulfuric acid is mixed with water.

$Question 12, shown as an image$

Explain how this equation shows that sulfuric acid is a strong acid.

[1]

Answer

(b)

Mia does a titration.

She puts the sulfuric acid in a burette.

She measures out 25.0 cm³ of 0.100 mol / dm³ NaOH.

(b)(i)

[1]

Answer

(b)(ii)

Calculate the number of moles in 25.0 cm³ of 0.100 mol / dm³ NaOH. (ii)

Use the equation: concentration (mol / dm³) = number of moles of solute ÷ volume (dm³

[3]

Answer

(b)(iii)

This is an equation for sulfuric acid reacting with NaOH.

$Question 12, shown as an image$

Mia finds that 24.5 cm³ of H₂SO₄ reacts exactly with the NaOH.

Calculate the concentration of the sulfuric acid in the burette in mol / dm³.

Use the equation: concentration (mol / dm³) = number of moles of solute ÷ volume (dm³

Give your answer to 2 significant figures.

Concentration =........ mol / dm³

[3]

Answer

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OCR J258 · Paper 3

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Question 11

Question 12