OCR GCSE Chemistry B (21st Century) Paper 3 June 2022 question paper

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Mia investigates the rate of reaction when zinc reacts with dilute sulfuric acid. She adds zinc pieces to dilute sulfuric acid at room temperature.

Fig. 1.1 shows the apparatus she uses:

(a)

Complete the symbol equation for the reaction.

Include a state symbol.

$Question 1, shown as an image$

[2]

Answer

(b)

Mia measures the volume of gas in the gas syringe every two minutes.

Fig. 1.2 shows a graph of her results:

(b)(i)

Calculate the rate of reaction during the first minute, using Fig. 1.2.

Give your answer in cm³ / s.

Rate of reaction =........ cm³ / s

[3]

Answer

(b)(ii)

Explain why the mass of the flask and its contents decreases during the reaction.

[1]

Answer

(c)

Mia repeats the experiment at the same temperature. She adds a few drops of blue copper sulfate.

Her results show that:

• more gas is produced in the first minute, than in the first experiment.

• the blue colour changes to colourless during the reaction.

Mia makes a statement about the results:

How do the results support Mia’s statement?

Explain your answer.

[3]

Answer

(d)

Mia repeats the experiment at a higher temperature.

Which statements explain why the reaction is faster at a higher temperature?

Tick (✓) two boxes.

$Question 1, shown as an image$

[2]

Answer

(a)

Complete the table by adding the two missing properties of clay ceramics.

[2]

Answer

(b)

Layla has three different water jugs. The jugs are made from aluminium, poly(ethene) and pottery (clay ceramic).

Draw lines to connect each material with its correct property.

Material
Property of jug

[3]

Answer

(c)

Poly(ethene) is made from ethene.

Complete the equation by drawing the structure of the repeating unit of poly(ethene).

[1]

Answer

(d)

Genes are made from the natural polymer DNA.

Which monomers make DNA?

Tick (✓) one box.

$Question 2, shown as an image$

[1]

Answer

The Earth’s early atmosphere contained mostly carbon dioxide and water vapour.

(a)

As the Earth cooled, the oceans formed. Water vapour condensed from gas to liquid.

The particle model can explain properties of gases and liquids.

Which statement is correct?

Tick (✓) one box.

$Question 3, shown as an image$

[1]

Answer

(b)

The particle model assumes molecules of water and carbon dioxide are inelastic spheres. This is a limitation of the particle model.

Water changes state at 100 °C. Carbon dioxide changes state at –79 °C.

Which statement explains another limitation of the particle model in relation to changes of state? Tick (✓) one box.

$Question 3, shown as an image$

[1]

Answer

(c)

Gradually, plants began to grow on Earth. Explain how this affected the composition of the atmosphere.

[2]

Answer

(d)

The graph shows how the percentage of carbon dioxide in the atmosphere has changed over time:

Ling and Ali discuss the graph:

Explain why Ling is wrong and Ali is correct.

Ling........

Ali........

[2]

Answer

When hydrogen burns, energy is transferred to the surroundings.

(a)

What word describes a reaction that releases energy to the surroundings?

[1]

Answer

(b)

The equation for the reaction is:

$Question 4, shown as an image$

Complete Fig. 4.1 to show the reaction profile for this reaction. Include on Fig. 4.1:

• the formulae of the reactants and products

• a label for the activation energy.

[2]

Answer

(c)

Which statement describes the activation energy?

Tick (✓) one box.

$Question 4, shown as an image$

[1]

Answer

(d)

[3]

Answer

Iodine is a halogen. It is an element in Group 17 (7) of the Periodic Table.

(a)

Which property shows iodine is a non-metal?

Tick (✓) one box.

$Question 5, shown as an image$

[1]

Answer

(b)

1.00 cm³ of iodine has a mass of 4.93 g. (b)

Calculate the volume of 1.00 mol of I₂.

$Question 5, shown as an image$

Give your answer to 1 decimal place.

[3]

Answer

(c)

Sodium iodide solution reacts with chlorine. This is a symbol equation for the reaction:

$Question 5, shown as an image$

(c)(i)

What would you see when this reaction happens?

[1]

Answer

(c)(ii)

What information does this reaction show about the reactivity of the halogens?

[1]

Answer

(d)

An isotope of iodine has a mass number of 127.

How many neutrons and electrons does an atom of this isotope have?

Use the Data Sheet.

[2]

Answer

(e)

Phosphorus reacts with iodine to form a compound.

The compound contains 7.5% by mass of phosphorus. The rest of the compound is iodine.

Determine the formula of the compound.

$Question 5, shown as an image$

[3]

Answer

In industry, crude oil fractions can be cracked to make alkenes.

(a)

Which statement explains why crude oil fractions are cracked?

Tick (✓) one box.

$Question 6, shown as an image$

[1]

Answer

(b)

Bromine reacts with ethene.

Fig. 6.1 shows the fully displayed formula of ethene:

Fig. 6.1

Draw the fully displayed formula of the product made when bromine reacts with ethene.

[1]

Answer

(c)(i)

[2]

Answer

(c)(ii)

A carboxylic acid can be made by oxidising ethanol.

Name the carboxylic acid made by oxidising ethanol.

[1]

Answer

(c)(iii)

Draw the fully displayed formula of the carboxylic acid made by oxidising ethanol.

[1]

Answer

(d)

Ethanol boils at 78 °C. Ethene boils at –104 °C.

Which statement explains why the boiling points are different?

Tick (✓) one box.

$Question 6, shown as an image$

[1]

Answer

(a)

Iron ore contains iron oxide. Iron can be made from iron ore. This is a symbol equation for the reaction:

$Question 7, shown as an image$

(a)(i)

Complete the half equation to show what happens to iron in this reaction.

$Question 7, shown as an image$

[1]

Answer

(a)(ii)

[1]

Answer

(b)

Calculate the percentage by mass of iron present in iron oxide, Fe₂O₃.

Give your answer to 3 significant figures.

[3]

Answer

(c)

Iron can be made into steel. The main disadvantage of steel is that it rusts.

Explain one method of preventing steel from rusting.

[2]

Answer

(d)

Used steel is collected and recycled. Recycling used steel has advantages and disadvantages.

Suggest one advantage and one disadvantage of recycling used steel.

Advantage........

Disadvantage........

[2]

Answer

Magnesium reacts with iron sulfide. This is a symbol equation for the reaction:

$Question 8, shown as an image$

(a)

What information does this reaction give about the reactivity of magnesium?

[1]

Answer

(b)

Magnesium sulfide, MgS is an ionic compound which contains the ions Mg²⁺ and S^2–. (b)

Explain why magnesium sulfide has a high melting point.

[2]

Answer

(c)

[2]

Answer

Alex adds the same volume of dilute sulfuric acid to different samples of zinc carbonate. The reaction fizzes.

(a)

Name the gas that causes the fizzing.

[1]

Answer

(b)

Table 9.1 shows Alex’s results:

(b)(i)

Explain why the rates of Experiment 1 and Experiment 2 are different in Table 9.1.

Use ideas about particles in your answer.

[2]

Answer

(b)(ii)

Relative average rate is the number of times faster one reaction is compared to another.

Calculate the relative average rate of Experiment 2, compared to Experiment 1.

[2]

Answer

(c)

Alex does two more experiments, Experiment 3 and Experiment 4.

The results are shown in Table 9.2.

Complete Table 9.2 by predicting the time taken for the reactions to stop fizzing.

[2]

Answer

Nina is given some diluted drain cleaner called ‘Drainclear’. ‘Drainclear’ contains sodium hydroxide.

Nina titrates 25.0 cm³ of diluted ‘Drainclear’ with dilute hydrochloric acid and an indicator.

(a)

Nina uses a burette to measure out the dilute hydrochloric acid in the titration.

Nina wants to minimise errors in her method.

Describe one thing she should do when taking burette readings.

[1]

Answer

(b)

The table shows Nina’s results:

	Rough	Titration 1	Titration 2	Titration 3
2nd reading (cm³)	14.05	20.55	10.60	22.05
1st reading (cm³)	3.00	10.05	0.05	11.60
Volume (cm³)	11.05	10.50	10.55	10.45
Mean (cm³)			10.50

Explain why Nina’s results are repeatable but not reproducible.

[2]

Answer

(c)

In her titration, Nina used 25.0 cm³ of diluted ‘Drainclear’ with 0.20 mol / dm³ hydrochloric (c) acid. A symbol equation for the reaction is:

$Question 10, shown as an image$

Calculate the concentration of sodium hydroxide, NaOH, in the diluted ‘Drainclear’.

$Question 10, shown as an image$

Use Nina’s mean result of 10.50 cm³.

Concentration of sodium hydroxide =........ mol / dm³

[3]

Answer

(d)

Nina says:

‘I would have preferred my titration result to be larger than 10.50 cm³. This would reduce the percentage uncertainty in my titration result.’

Explain how Nina could get a larger titration result without changing her apparatus.

[2]

Answer

Aluminium and chlorine can be made by electrolysis.

(a)

Aluminium is made by the electrolysis of molten aluminium oxide.

(a)(i)

At which electrode is aluminium formed?

[1]

Answer

(a)(ii)

Give one reason for your answer to (a)(i).

[1]

Answer

(b)

Some elements are extracted using electrolysis.

(b)(i)

Explain why hydrogen, not sodium, is made at the negative electrode when sodium chloride solution is electrolysed.

[1]

Answer

(b)(ii)

Write the half equation for the formation of hydrogen at the negative electrode.

[2]

Answer

(c)

Kareem electrolyses sodium chloride solution. Hydrogen gas and chlorine gas are made.

Describe what Kareem needs to do to measure the volumes of hydrogen gas and chlorine gas made.

You may add to the diagram to help explain your answer. The diagram is not complete.

[2]

Answer

Eve has some copper sulfate crystals. The formula of copper sulfate is CuSO₄.

(a)

Eve says, ‘Copper sulfate is a mixture of several elements. It is not a pure substance.’

Explain why Eve is wrong.

[2]

Answer

(b)

Eve dissolves the copper sulfate crystals in water. She does two tests on the copper sulfate solution.

(b)(i)

In test 1 she adds sodium hydroxide solution to the solution of copper sulfate. She sees a blue precipitate of copper hydroxide.

Write a word equation for the formation of copper hydroxide.

[1]

Answer

(b)(ii)

In test 2 she adds acidified barium chloride solution to the solution of copper sulfate. She sees a white precipitate of barium sulfate.

Write an ionic equation for the formation of the white precipitate.

[2]

Answer

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