OCR GCSE Chemistry B (21st Century) Paper 3 June 2024 question paper

Fertilisers are used to increase the growth of plants.

They are added to soil to provide essential plant nutrient elements.

(a)

Nitrogen is one essential plant nutrient element.

Name two other essential plant nutrient elements.

[2]

Answer

(b)

(b)(i)

State one disadvantage of the over-use of synthetic fertilisers.

[1]

Answer

(b)(ii)

Suggest why farmers still use synthetic fertilisers despite their disadvantages.

[1]

Answer

(c)

[4]

Answer

Sodium chloride is an ionic compound.

(a)

(a)(i)

Describe the attraction between ions in sodium chloride.

[2]

Answer

(a)(ii)

[2]

Answer

(a)(iii)

Fig. 2.2 shows the dot and cross diagram for sodium chloride.

Complete Fig. 2.2 to show the structure and charge of the chloride ion.

Sodium atom
Chlorine atom
Sodium ion
Chloride ion

[2]

Answer

(b)

How does the arrangement of electrons in atoms of sodium and chlorine relate to their group and period in the Periodic Table?

[2]

Answer

(c)

An atom of sodium has an atomic number of 11 and a mass number of 23.

State the number of protons, neutrons and electrons in a sodium atom.

[2]

Answer

A student uses paper chromatography to check the purity of two dyes used to make coloured plastics.

The diagram shows a chromatogram for the two dyes.

(a)

Explain why hexane rather than water must be used as the solvent for these dyes.

[1]

Answer

(b)

Calculate the Rf value of dye B.

Give the answer to an appropriate number of significant figures.

[4]

Answer

(c)

The student wants to check that there are no colourless substances in the dyes.

What must be sprayed onto the chromatogram so any colourless substances can be seen?

[1]

Answer

Chloride ions, bromide ions and iodide ions are halide ions.

A student tests three solutions, A, B, and C, to find out whether they contain halide ions.

The student adds acidified dilute silver nitrate to the three solutions.

The table below shows their results.

Solution	Observation after adding acidified dilute silver nitrate
A	White precipitate
B	No precipitate
C	Yellow precipitate

(a)

What conclusions can the student make about the ions present in each solution?

Solution A........

Solution B........

Solution C........

[3]

Answer

(b)

Complete the word equation and ionic equation for the reaction between solutions of silver ions and bromide ions.

You need to:

• add the name and the formula for the product

• add the missing state symbols.

silver ions + bromide ions $fraction$ ........

$Question 4, shown as an image$

[3]

Answer

(c)

Before the tests, silver nitrate solution is acidified by adding a dilute acid.

Explain why dilute hydrochloric acid is not a suitable acid to use to acidify the silver nitrate solution.

[1]

Answer

Some metals can be extracted from their ores using electrolysis.

(a)

(a)(i)

[2]

Answer

(a)(ii)

Why is the formation of copper from copper ions a reduction reaction?

[1]

Answer

(a)(iii)

Explain why copper and not hydrogen is formed at the cathode.

[2]

Answer

(a)(iv)

Describe one observation that can be seen as the electrolysis proceeds.

[1]

Answer

(b)

Aluminium is extracted from aluminium oxide by electrolysis.

Oxygen is also made in this process.

(b)(i)

Complete the balanced symbol equation for the electrolysis of aluminium oxide.

$Question 5, shown as an image$

[2]

Answer

(b)(ii)

[2]

Answer

(b)(iii)

Describe a test to identify oxygen.

[2]

Answer

(a)

The equation for the reaction of calcium carbonate with dilute hydrochloric acid is:

$Question 6, shown as an image$

(a)(i)

Write the chemical formula for X.

[1]

Answer

(a)(ii)

The mass decreases during the reaction.

Explain why.

[2]

Answer

(b)

100 cm³ of dilute hydrochloric acid contains 5.0 g of HCl. (b)

(b)(i)

Calculate the number of moles of HCl in 100 cm³ of dilute hydrochloric acid. (i)

Relative atomic masses (A_r): H = 1.0 Cl = 35.5

$Question 6, shown as an image$

[3]

Answer

(b)(ii)

There are 6.0 × 10²³ atoms in one mole of atoms. (ii)

How many atoms are in 4 moles of HC l ?

$Question 6, shown as an image$

1.2 × 10²⁴ 2.4 × 10²⁴ 4.8 × 10²⁴ 8 × 10²³

[1]

Answer

Aqueous hydrogen peroxide breaks down slowly to form oxygen gas and water.

$Question 7, shown as an image$

(a)

[1]

Answer

(b)

Explain why increasing the concentration of the aqueous hydrogen peroxide also speeds up the reaction.

Use ideas about particles.

[2]

Answer

(c)

In one experiment, 0.1 moles of oxygen is collected when hydrogen peroxide decomposes.

Calculate the volume of 0.1 moles of oxygen at room temperature and pressure.

$Question 7, shown as an image$

Give your answer in cm³.

[3]

Answer

Fossil fuels are used as energy sources.

(a)

Natural gas contains an alkane with the formula CH₄.

(a)(i)

Name this alkane.

[1]

Answer

(a)(ii)

Combustion of natural gas increases the temperature of the surroundings.

Name of the type of reaction that increases the temperature of the surroundings.

[1]

Answer

(a)(iii)

Incomplete combustion occurs when not enough oxygen is present.

Name one pollutant caused by the incomplete combustion of natural gas.

[1]

Answer

(b)

[3]

Answer

(c)

Hydrogen fuel cells can be used in cars, but many cars use fossil fuels, such as diesel.

The table shows information about hydrogen and diesel.

(c)(i)

Diesel is a hydrocarbon.

Name the products formed during complete combustion of diesel.

[1]

Answer

(c)(ii)

Evaluate the impact on the environment of producing and using hydrogen and diesel as fuels.

[2]

Answer

(c)(iii)

Explain why the density of hydrogen and diesel are very different.

Use data from the table.

[2]

Answer

The table shows some information about the homologous series of alcohols.

(a)

[2]

Answer

(b)

Alcohols oxidise to form carboxylic acids.

(b)(i)

Name the carboxylic acid formed when propanol is oxidised.

[1]

Answer

(b)(ii)

Draw the displayed formula of the carboxylic acid formed when propanol is oxidised.

Show all the bonds.

[1]

Answer

Black silver oxide powder decomposes when heated to form silver and oxygen gas.

The balanced symbol equation for the reaction is:

$Question 10, shown as an image$

(a)

Calculate the theoretical yield of silver made when 250 g of silver oxide completely decomposes.

Relative atomic mass (A_r): O = 16 Ag = 108

Give your answer to 3 significant figures.

[4]

Answer

(b)

The actual yield of silver in an experiment is 215 g.

Some black silver oxide powder remains visible after the experiment.

Suggest two ways the experiment could be changed to increase the actual yield.

[2]

Answer

(a)

[1]

Answer

(b)

(b)(i)

The student says that all concentrated acids are strong acids and all dilute acids are weak acids.

Explain why they are incorrect.

[1]

Answer

(b)(ii)

The student adds a carbonate to three dilute acids, A, B and C, with the same concentration.

They record the pH of each acid and the time taken for each reaction to finish (the reaction time).

The table shows the results.

Acid	pH	Reaction time (s)
A	1	10
B	3	200
C	5	1000

Which acid is the weakest acid?

Explain your answer.

Use:

• data from the table

• ideas about hydrogen ions.

[3]

Answer

(c)

(c)(i)

Describe how to use Universal indicator to measure the pH of a solution.

[1]

Answer

(c)(ii)

A solution of pH 1 has a hydrogen ion concentration of 0.1 mol / dm³. (ii)

What is the hydrogen ion concentration of a solution of pH 3?

$Question 11, shown as an image$

1 × 10^–1 mol / dm³ 1 × 10^–2 mol / dm³ 1 × 10^–3 mol / dm³ 1 × 10^–4 mol / dm³

[1]

Answer

Group 7(17) of the Periodic Table contains non-metals called halogens.

(a)

The table shows the properties of three Group 7(17) elements at room temperature and pressure.

Complete the table.

Element	Colour	State at room temperature
Chlorine	Pale green	......................................
Bromine	......................................	Liquid
Iodine	Grey	Solid

[2]

Answer

(b)

A student adds aqueous sodium iodide to aqueous chlorine.

The balanced symbol equation for the reaction is:

$Question 12, shown as an image$

(b)(i)

Explain what the student observes when the reaction takes place.

[3]

Answer

(b)(ii)

Write an ionic equation for the reaction.

Use the symbol equation to help you.

[1]

Answer

OCR J258 · Paper 3

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12