OCR GCSE Chemistry A (Gateway) Paper 3 Higher November 2021 question paper J248/03

1h 45m 90 marks

22 questions

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Which statement about the subatomic particles in an atom is correct?

A Electrons have a relative mass of one.

B Neutrons and electrons are both found in the nucleus.

C Neutrons have a positive charge.

D Protons have a relative mass of one.

$Question 1, shown as an image$

[1]

Answer

[1]

Answer

Which statement describes ionic bonding?

A Electrons are delocalised.

B Electrons are shared between atoms.

C Electrons are transferred from a metal to a non-metal.

D Electrons are transferred from a non-metal to a metal.

$Question 3, shown as an image$

[1]

Answer

Oxygen has three naturally occurring isotopes.

Which statement about isotopes of oxygen is correct?

A All isotopes of oxygen have 8 electrons and 8 neutrons.

B All isotopes of oxygen have 8 electrons and 8 protons.

C All isotopes of oxygen have 8 neutrons and 8 protons.

D All isotopes of oxygen have the same mass number.

$Question 4, shown as an image$

[1]

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Which type of reaction occurs when the temperature of the surroundings increases?

A Crystallisation

B Endothermic

C Exothermic

D Reduction

$Question 5, shown as an image$

[1]

Answer

Copper oxide reacts with carbon. Oxidation takes place in this reaction.

$Question 6, shown as an image$

Which substance is oxidised ?

A C

B CO₂

C Cu

D CuO

$Question 6, shown as an image$

[1]

Answer

Sulfuric acid, H₂SO₄, reacts with sodium hydroxide, NaOH, in a neutralisation reaction.

What are the products of this reaction?

A Sodium sulfate and hydrogen

B Sodium sulfate and water

C Sodium sulfate, hydrogen and oxygen

D Sodium sulfate, hydrogen and water

$Question 7, shown as an image$

[1]

Answer

Which statement is a reason that nanoparticles can be used as catalysts?

A Nanoparticles are safe and have no risks.

B Nanoparticles are smaller than atoms.

C Nanoparticles have a large surface area to volume ratio.

D Nanoparticles have a small surface area to volume ratio.

$Question 8, shown as an image$

[1]

Answer

Sodium reacts with hydrochloric acid to give sodium chloride and hydrogen gas.

What is the balanced symbol equation for this reaction?

$Question 9, shown as an image$

[1]

Answer

The table shows melting points and boiling points for some Group 7 elements.

Element	Melting point (°C)	Boiling point (°C)
Fluorine	-220	-188
Chlorine	-102	-34
Bromine	-7	59
Iodine	114	184

Which statement is correct at room temperature?

A Bromine is a liquid and chlorine is a solid.

B Fluorine is a gas and bromine is a liquid.

C Fluorine is a gas and iodine is a liquid.

D Iodine is a gas and fluorine is a solid.

$Question 10, shown as an image$

[1]

Answer

The empirical formula of a hydrocarbon is CH₂.

The relative formula mass of the hydrocarbon is 126.0.

What is the molecular formula of the hydrocarbon?

A C₇H₁₄

B C₈H₁₆

C C₉H₁₈

D C₁₀H₂₀

$Question 11, shown as an image$

[1]

Answer

Magnesium reacts with oxygen. Magnesium oxide is made.

The balanced symbol equation is shown.

$Question 12, shown as an image$

Calculate how much magnesium is needed to make 10.0 g of magnesium oxide.

A 4.0 g

B 6.0 g

C 10.0 g

D 16.6 g

$Question 12, shown as an image$

[1]

Answer

A student investigates if an unknown liquid sample is pure.

Which method should the student use?

A Filter the sample to see if any solid can be separated.

B Gas chromatography.

C Measure the boiling point of the sample.

D Titration.

$Question 13, shown as an image$

[1]

Answer

Which statement about covalent bonding is not correct?

A Covalent bonds are broken when a compound changes state from a liquid to a gas.

B Covalent bonds are strong.

C Covalent bonds can be found in both simple compounds and giant structures.

D Covalent bonds share electrons between atoms.

$Question 14, shown as an image$

[1]

Answer

[1]

Answer

The table shows carbon can exist as several different structures called allotropes.

Allotrope	Covalent bonds
Diamond	.....................
Graphite	.....................
Graphene	3

(a)

Complete the table to show how many covalent bonds carbon forms in these allotropes.

[2]

Answer

(b)(i)

Diamond can be used as a cutting tool because it is so hard.

Explain why diamond is so hard.

Use ideas about structure and bonding in diamond in your answer.

[2]

Answer

(b)(ii)

Graphite can be used as a lubricant because it is slippery.

Explain why graphite is slippery.

Use ideas about structure and bonding in graphite in your answer.

[2]

Answer

(c)

Explain why carbon forms many other compounds. Use ideas about the bonding in carbon compounds in your answer.

[2]

Answer

The table shows information about some properties of four substances.

Substance	Melting point (°C)	Boiling point (°C)	Solubility in water	Does the substance conduct electricity?
M	-98	65	Soluble	No
N	-114	78	Soluble	No
O	661	1304	Soluble	Only when molten or dissolved
P	1085	2562	Insoluble	Yes

(a)

Which diagram shows the apparatus that should be used to separate a mixture of substance M and substance N ? Tick (✓) one box.

[1]

Answer

(b)(i)

Describe a method that could be used to separate a mixture of substance O and substance P to obtain pure samples.

[3]

Answer

(b)(ii)

A student separates substance O from a mixture.

They start with 6.2 g of the mixture and obtain 2.6 g of pure substance O.

Calculate the mass of pure substance O that could be separated from 10.0 g of the mixture.

Give your answer to 3 significant figures.

[3]

Answer

(c)

Draw lines to connect each substance with its correct type of structure and bonding.

[3]

Answer

All chemical reactions follow the law of conservation of mass.

(a)

State the law of conservation of mass.

[1]

Answer

(b)

A student investigates the reaction of magnesium carbonate with dilute hydrochloric acid. Look at the equation for the reaction.

$Question 18, shown as an image$

Describe the movement of the magnesium carbonate particles used in this reaction.

Use ideas about the particle model in your answer.

[2]

Answer

(c)

The student sets the experiment up on a balance as shown in the diagram.

(c)(i)

Explain why the mass on the balance decreases as the reaction occurs.

Use ideas about the particle model in your answer.

[2]

Answer

(c)(ii)

The particle model is not a perfect representation of the three states of matter.

Describe two limitations of the particle model.

[2]

Answer

(d)

(d)(i)

Explain why the student’s method does not work.

[1]

Answer

(d)(ii)

Suggest two ways the method could be changed to produce a pure, dry sample of magnesium chloride, MgCl₂.

[2]

Answer

(a)

Theories about atoms have developed as new evidence has been discovered.

J.J. Thomson’s model of the atom was called the “plum pudding” model.

(a)(i)

Describe two differences between the current understanding of the structure of the atom and J.J. Thomson’s “plum pudding” model.

[2]

Answer

(a)(ii)

[2]

Answer

(b)(i)

Calculate the average mass of one atom of neon, Ne.

The Avogadro constant has a value of 6.02 maths symbol 10²³.

Give your answer to 3 significant figures.

[3]

Answer

(b)(ii)

Three isotopes of neon are shown.

How many neutrons does an atom of neon-21 contain?

[1]

Answer

(b)(iii)

Calculate how many moles of neon there are in 101 g of neon.

(The relative atomic mass, A_r, of Ne is 20.2.)

[2]

Answer

(c)

Neon is in Group 0 of the Periodic Table. Lithium is in Group 1 of the Periodic Table.

Explain, in terms of electronic structure, why elements in Group 1 are more reactive than elements in Group 0.

[2]

Answer

(a)

In both experiments, copper is deposited at the cathode.

Describe a difference between the electrolysis of copper sulfate solution using inert graphite electrodes and non-inert copper electrodes.

[1]

Answer

(b)

A student investigates the electrolysis of sodium chloride solution.

(b)(i)

[2]

Answer

(b)(ii)

State the name of the substance made at the anode.

[1]

Answer

(b)(iii)

[2]

Answer

(c)

The student investigates materials to use as inert electrodes in the electrolysis of aqueous sodium chloride.

They compare four materials A, B, C, and D. Their results are shown in the table.

Material	Soluble in water?	Does it conduct electricity?	Density (g / cm³)
A	yes	yes	7.87
B	no	yes	12.41
C	no	only when molten	2.17
D	yes	no	1.54

Which material, A, B, C or D, is the most suitable for use as an inert electrode?

Explain your answer.

Material........

Explanation........

[3]

Answer

(a)

[6]

Answer

(b)

When the painkiller is sold to the public, it is sold as a formulation, not as a pure substance.

Explain how a formulation and a mixture are different.

[1]

Answer

(c)

The painkiller is an acid.

(c)(i)

[3]

Answer

(c)(ii)

The scientist titrates a solution of the painkiller against a solution of sodium hydroxide, NaOH.

The titration curve is shown.

Volume of NaOH solution added (cm³)

The scientist concludes that the painkiller is a strong acid.

Is the scientist correct?

Explain your answer.

[2]

Answer

Hydrogen sulfide, H₂S, reacts with oxygen, O₂, to form sulfur dioxide, SO₂, and water.

The balanced symbol equation is shown.

$Question 22, shown as an image$

(a)

A scientist sets up the reaction so that hydrogen sulfide is the limiting reactant.

(a)(i)

Explain what is meant by the term limiting reactant.

[1]

Answer

(a)(ii)

Explain what effect a limiting reactant has on a reaction.

[1]

Answer

(b)

Calculate the mass of sulfur dioxide made from 102.3 g of hydrogen sulfide.

(The relative atomic mass, A_r, of H is 1.0, of O is 16.0 and of S is 32.1).

[3]

Answer

(c)

The reaction of hydrogen sulfide with oxygen is shown using displayed formulae.

$Question 22, shown as an image$

The table shows the bond energies of the bonds in the reactants and products.

Bond	Bond energy (kJ / mol)
S–H	347
O=O	494
S=O	523
H–O	459

The energy needed to break the bonds in two moles of hydrogen sulfide is 1388 kJ.

Use the bond energies to calculate the energy change of the reaction when two moles of hydrogen sulfide react with oxygen.

Give your answer to 3 significant figures.

[4]

Answer

(d)

Sulfur dioxide reacts with oxygen to form sulfur trioxide.

The reaction profile is shown.

$Question 22, shown as an image$

(d)(i)

[2]

Answer

(d)(ii)

Sulfur trioxide reacts with water to form sulfuric acid.

• A scientist measures the pH of some dilute sulfuric acid. The pH is 2.

• The scientist makes a solution by adding 990 cm³ of water to 10 cm³ of the dilute sulfuric acid.

Calculate the pH of the solution.

[3]

Answer

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OCR J248 · Paper 3

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

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Question 9

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Question 22