Skip to content

Paper Together: sit a paper in a room with your friends.See how it works

Titrations and their calculations: GCSE Combined Science Chemistry practice questions

Higher tier content · Grade 8

A second set of questions on titrations and their calculations. They are different from the ones on the topic page. Try each, then open the answer and compare your working.

More questions

Question 1 Medium

25.0 cm³ of 0.100 mol/dm³ NaOH needs 20.0 cm³ of hydrochloric acid. Calculate the concentration of the acid in mol/dm³.

Show answer

Answer: 0.125 mol/dm³

  1. Moles of NaOH = 0.100 × 0.0250 = 0.00250.
  2. Concentration of HCl = 0.00250 ÷ 0.0200 = 0.125.

Question 2 Medium

Convert a concentration of 0.125 mol/dm³ of HCl into g/dm³. Mr of HCl = 36.5. Give your answer to 3 significant figures.

Show answer

Answer: 4.56 g/dm³

  1. Multiply mol/dm³ by Mr.
  2. 0.125 × 36.5 = 4.5625.

Question 3 Medium

Calculate the moles of sodium hydroxide in 25.0 cm³ of 0.200 mol/dm³ NaOH.

Show answer

Answer: 0.00500 mol

  1. 25.0 cm³ = 0.0250 dm³.
  2. Moles = 0.200 × 0.0250 = 0.00500.

Question 4 Medium

A solution of NaOH has a concentration of 0.250 mol/dm³. Calculate its concentration in g/dm³. Mr of NaOH = 40.

Show answer

Answer: 10.0 g/dm³

  1. Multiply mol/dm³ by Mr.
  2. 0.250 × 40 = 10.0.

Question 5 Hard

H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. 25.0 cm³ of 0.200 mol/dm³ NaOH needs 20.0 cm³ of H₂SO₄. Calculate the concentration of the acid in mol/dm³.

Show answer

Answer: 0.125 mol/dm³

  1. Moles of NaOH = 0.200 × 0.0250 = 0.00500.
  2. Moles of H₂SO₄ = 0.00250.
  3. Concentration = 0.00250 ÷ 0.0200 = 0.125.

Question 6 Hard

20.0 cm³ of 0.0500 mol/dm³ sulfuric acid is neutralised by NaOH solution. Calculate the moles of NaOH needed. H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O

Show answer

Answer: 0.00200 mol

  1. Moles of H₂SO₄ = 0.0500 × 0.0200 = 0.00100.
  2. The ratio is 1 : 2, so NaOH = 0.00200.

Question 7 Hard

25.0 cm³ of potassium hydroxide is neutralised by 15.0 cm³ of 0.200 mol/dm³ HCl. Calculate the concentration of the potassium hydroxide in g/dm³. Mr of KOH = 56.

Show answer

Answer: 6.72 g/dm³

  1. Moles of HCl = 0.200 × 0.0150 = 0.00300.
  2. KOH concentration = 0.00300 ÷ 0.0250 = 0.120 mol/dm³.
  3. In g/dm³: 0.120 × 56 = 6.72.

Question 8 Hard

A student says a rough titre should be included in the mean. Explain why this is wrong.

Show answer

Answer: it is less accurate because the acid was added quickly

  1. The rough titre is only used to find the approximate end-point.
  2. It is less accurate because the acid is added quickly.

Question 9 Medium

Calculate the mean of the concordant titres 15.10, 15.20 and 15.15 cm³.

Show answer

Answer: 15.15 cm³

  1. (15.10 + 15.20 + 15.15) ÷ 3.
  2. 45.45 ÷ 3 = 15.15.

Question 10 Hard

25.0 cm³ of sulfuric acid is neutralised by 30.0 cm³ of 0.100 mol/dm³ sodium hydroxide. H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. Calculate the concentration of the acid in mol/dm³.

Show answer

Answer: 0.0600 mol/dm³

  1. Moles of NaOH = 0.100 × 0.0300 = 0.00300.
  2. Moles of H₂SO₄ = 0.00300 ÷ 2 = 0.00150.
  3. Concentration = 0.00150 ÷ 0.0250 = 0.0600.

Quick checks

Short questions with options. Choose one before you open the answer.

Check 1

What is a titration?

Show answer

A method to find the volumes of two solutions that exactly react.

Check 2

Which apparatus measures 25.0 cm³ accurately?

Show answer

A pipette.

Check 3

What does the burette measure?

Show answer

The volume of solution added.

Check 4

What is the end-point?

Show answer

The point where the indicator just changes colour.

Check 5

What is the titre?

Show answer

The volume added from the burette to reach the end-point.

Check 6

What does concordant mean?

Show answer

Results within 0.10 cm³ of each other.

Check 7

What should you do with the rough titration?

Show answer

Leave it out of the mean.

Check 8

What colour is phenolphthalein in alkali?

Show answer

Pink.

Check 9

What colour is methyl orange in acid?

Show answer

Red.

Check 10

Why not use universal indicator in a titration?

Show answer

The colour change is gradual.

Check 11

What is the equation for moles from concentration?

Show answer

Moles = concentration × volume in dm³.

Check 12

How many moles of NaOH react with 1 mole of H₂SO₄?

Show answer

2.

Check 13

How do you change mol/dm³ into g/dm³?

Show answer

Multiply by the relative formula mass.

Check 14

Why add the acid drop by drop near the end?

Show answer

To avoid overshooting the end-point.

Check 15

What do you do to cm³ before using it in a concentration calculation?

Show answer

Divide by 1000 to get dm³.

Check 16

What does a pipette do in a titration?

Show answer

It measures one fixed volume, such as 25.0 cm³, accurately.

Check 17

What is an indicator?

Show answer

A dye that changes colour to show the end-point.

Check 18

Why stand the flask on a white tile?

Show answer

The colour change is easier to see.

Check 19

Why rinse the burette with the acid before use?

Show answer

So that left-over water does not dilute the acid.

Check 20

What is an anomalous result?

Show answer

A result that does not fit with the others.

Check 21

What is the rough titration for?

Show answer

To find the approximate end-point.

Check 22

How many dm³ are in 25.0 cm³?

Show answer

0.0250 dm³.

Check 23

How do you find concentration in mol/dm³ from moles?

Show answer

Divide the moles by the volume in dm³.

Check 24

Where do you read the burette?

Show answer

At eye level, at the bottom of the meniscus.

Check 25

Why do you add the acid drop by drop near the end-point of a titration?

Show answer

So you do not overshoot, which would make the titre too large.

Keep going with Titrations and their calculations

Practise free

Start free

Yumio is not affiliated with, endorsed by or connected to AQA, Pearson Edexcel or any other exam board.

Practise free