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OCR GCSE Combined Science

Topic questions Quantitative chemistry Concentration of solutions

Concentration of solutions

5 questions · 43 marks · about 50 minutes

Concentration of solutions questions

TopicConcentration of solutions

OCR J250 Concentration of solutions 5 questions

Chemistry Paper 9 June 2025 Higher tier, Question 10 1 mark

How many grams of NaOH are found in 50 cm3 of a 4 g / dm3 solution of NaOH(aq)? 10

A 0.08 g

B 0.2 g

C 2 g

D 80 g

Question 10, shown as an image
[1]
Reveal mark scheme Mark scheme for question 10

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 14 18 marks

Calcium is a metal found in Group 2 of the Periodic Table.

(a)

Draw the arrangement of electrons in an atom of calcium.

[1]
Reveal mark scheme Mark scheme for question 14(a)
(b)

Calcium is a metal which can conduct electricity.

Describe the structure and bonding in a metal and explain why metals can conduct electricity.

You can include a diagram in your answer.

[4]
Reveal mark scheme Mark scheme for question 14(b)
(c)

Calcium reacts with water to form a solution of calcium hydroxide, Ca(OH)2, and hydrogen.

(c)(i)

Write the balanced symbol equation for the reaction of calcium with water.

Include state symbols in your equation.

[3]
Reveal mark scheme Mark scheme for question 14(c)(i)
(c)(ii)

A solution of calcium hydroxide is also called limewater.

Name the gas limewater is used as a test for.

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

Calculate the number of moles in 1.88 g of calcium hydroxide.

Give your answer to 2 significant figures.

Relative atomic mass (Ar): H = 1.0 O = 16.0 Ca = 40.1

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

Use your answer to part (d)(i) to calculate the concentration of calcium hydroxide in the solution formed.

Give your answer in mol / dm3.

Concentration of solution =........ mol / dm3

[2]
Reveal mark scheme Mark scheme for question 14(d)(ii)
(e)

A student adds an excess of dilute hydrochloric acid, HC l, to a solution of calcium hydroxide, Ca(OH)2.

(e)(i)

Write the balanced ionic equation for the reaction of dilute hydrochloric acid and a solution of calcium hydroxide.

[1]
Reveal mark scheme Mark scheme for question 14(e)(i)
(e)(ii)

Describe and explain how the pH of the solution of calcium hydroxide changes as the dilute hydrochloric acid is added until it is in excess.

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

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