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OCR GCSE Combined Science

Topic questions Chemical changes Strong and weak acids

Strong and weak acids

5 questions · 33 marks · about 40 minutes

Strong and weak acids questions

TopicStrong and weak acids

OCR J250 Strong and weak acids 5 questions

Chemistry Paper 9 June 2024 Higher tier, Question 14 11 marks

Figure for question 14
(a)

Write the formula of the molecules in the box for R to show a balanced reaction.

[2]
Reveal mark scheme Mark scheme for question 14(a)
(b)

Write the name and the formula of the compound in solution S.

[2]
Reveal mark scheme Mark scheme for question 14(b)
(c)

Name the type of reaction which happens between solutions P and Q.

[1]
Reveal mark scheme Mark scheme for question 14(c)
(d)

Which of the solutions in the diagram shows a strong acid?

Tick (✓) one box.

Question 14, shown as an image

Give two reasons for your answer.

[3]
Reveal mark scheme Mark scheme for question 14(d)
(e)

A student dissolves 2 g of a strong acid in 250 cm3 of water. (e)

Calculate the concentration of the solution formed in g / dm3.

Concentration of the solution =........ g / dm3

[3]
Reveal mark scheme Mark scheme for question 14(e)

Chemistry Paper 9 June 2023 Higher tier, Question 15 12 marks

(a)

Describe the difference between a strong acid and a weak acid.

[1]
Reveal mark scheme Mark scheme for question 15(a)
(b)

Hydrochloric acid, HC l (aq), is an example of a strong acid.

The graph shows the pH of a dilute hydrochloric acid solution at different concentrations.

Figure for question 15

Concentration of dilute hydrochloric acid solution (mol/dm3)

(b)(i)

Write the formula of the ion that gives the dilute hydrochloric acid solution the pH shown on the graph.

[1]
Reveal mark scheme Mark scheme for question 15(b)(i)
(b)(ii)

The pH of the dilute hydrochloric acid solution can be measured using either universal indicator or a pH meter.

Explain which method would be better to use for measuring the pH shown on the graph.

[2]
Reveal mark scheme Mark scheme for question 15(b)(ii)
(c)

Describe how the pH changes with the concentration of dilute hydrochloric acid solution on the graph.

[2]
Reveal mark scheme Mark scheme for question 15(c)
(d)

As the concentration of the dilute hydrochloric acid solution increases by a factor of ten, the pH of the solution decreases by one.

Use data from the graph to show that this statement is true.

[2]
Reveal mark scheme Mark scheme for question 15(d)
(e)

Calculate the mass of hydrochloric acid, HCl, in 100 cm3 of solution that gives a pH 1.5. (e)

Use data from the graph.

Give your answer to 2 significant figures.

Relative molecular mass (Mr): HCl = 36.5

[4]
Reveal mark scheme Mark scheme for question 15(e)

Chemistry Paper 9 June 2022 Higher tier, Question 6 1 mark

The table shows some information about four different acids.

AcidNumber of particles per cm3 of acid solutionDegree of ionisation (%)
Ahigh1
Blow1
Chigh100
Dlow100

Which acid is a dilute solution of a strong acid?

Question 6, shown as an image
[1]
Reveal mark scheme Mark scheme for question 6

Chemistry Paper 9 November 2020 Higher tier, Question 16 8 marks

Phosphoric acid, H3PO4, is a strong acid.

A student investigates how the pH of a solution of dilute phosphoric acid changes when a solution of calcium hydroxide is slowly added to it from a burette.

Figure for question 16

The student then calculates the concentration of hydrogen ions as the pH changes.

Table 16.1 shows the results of her experiment.

Figure for question 16
(a)

Explain why phosphoric acid is described as a strong acid.

[1]
Reveal mark scheme Mark scheme for question 16(a)
(b)

Explain why the solution of phosphoric acid used is described as dilute.

[1]
Reveal mark scheme Mark scheme for question 16(b)
(c)

Complete the balanced symbol equation for the reaction between phosphoric acid and calcium hydroxide.

Question 16, shown as an image
[2]
Reveal mark scheme Mark scheme for question 16(c)
(d)
Figure for question 16
[2]
Reveal mark scheme Mark scheme for question 16(d)
(e)
Figure for question 16
[2]
Reveal mark scheme Mark scheme for question 16(e)

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