Cambridge IGCSE Chemistry 0620 · Extended · Syllabus 2026-2028

Acid–Base Titrations Worked ExamplesIGCSE Chemistry 0620

Exam-style titration questions: the apparatus (burette, volumetric pipette, conical flask, white tile), choosing methyl orange or thymolphthalein and identifying the end-point, reading burettes and choosing concordant titres, concentration calculations with 1 : 1 and 1 : 2 ratios in mol/dm³ and g/dm³, making a soluble salt by titration, effects of errors on the titre, comparing concentrations, water of crystallisation and percentage purity.

This page has 12 exam-style IGCSE Chemistry 0620 acid–base titrations worked examples — 2 Core, 8 Extended and 2 Challenge, 5 with diagrams. Each one shows the full method step by step, the final answer in the form a marker expects, and an examiner tip on where marks are commonly lost.

Example 1CoreName titration apparatus; describe how the alkali is measured; choose an indicator and identify the end-point[6 marks]

Describing a titration: apparatus, indicator and end-point

The diagram shows apparatus used to titrate aqueous sodium hydroxide with dilute hydrochloric acid, using methyl orange indicator.

(a) Name P, Q and R.

(b) Name the apparatus used to put exactly $25.0\text{ cm}^3$ of the alkali into Q.

(c) Describe how the student adds the acid and how the end-point is identified.

(d) Give one reason why universal indicator is not used.

Example 2CoreMultiple choice: indicator and colour change at the end-point[1 mark]

Multiple choice: thymolphthalein colours in a titration

Aqueous potassium hydroxide is placed in a conical flask with a few drops of indicator. Dilute nitric acid is added from a burette until the end-point.

Which row is correct?

	indicator	colour at the start	colour at the end-point
A	thymolphthalein	colourless	blue
B	thymolphthalein	blue	colourless
C	universal indicator	purple	green
D	methyl orange	red	yellow

Example 3ExtendedRead burette scales to 0.05 cm³; record to 2 d.p.; subtract; select concordant results and average[5 marks]

Reading burettes and choosing concordant titres

The diagram shows the burette readings at the start and end of three accurate titrations.

(a) Record the initial and final readings and the titre for each run.

(b) Titres within $0.10\text{ cm}^3$ of each other are concordant. Calculate the mean titre to use in calculations.

Example 4ExtendedIdentify the end-point colour; purpose of white tile, swirling and dropwise addition[5 marks]

Methyl orange end-point and good titration technique

A student titrates aqueous sodium carbonate in a conical flask with dilute hydrochloric acid, using methyl orange. The diagram shows the colour of the flask at three stages.

(a) Which flask shows

(i) the start and

(ii) the end-point? Explain what flask 3 shows.

(b) State the purpose of the white tile.

(c) State what the student should do to the flask while adding the acid.

(d) Explain why the acid is added drop by drop near the end-point.

Example 5ExtendedTitre from burette readings; 1 : 1 calculation; dilution factor; convert mol/dm³ to g/dm³[6 marks]

Concentration of ethanoic acid in vinegar

A student dilutes a sample of vinegar exactly $10$ times with distilled water. $25.0\text{ cm}^3$ of the diluted vinegar is titrated with $0.100\text{ mol/dm}^3$ sodium hydroxide, using thymolphthalein. The burette readings are shown.

$\text{CH}_3\text{COOH(aq)} + \text{NaOH(aq)} \rightarrow \text{CH}_3\text{COONa(aq)} + \text{H}_2\text{O(l)}$

(a) Find the volume of sodium hydroxide used.

(b) Calculate the concentration of ethanoic acid in the diluted vinegar.

(c) Calculate the concentration of ethanoic acid in the original vinegar in $\text{mol/dm}^3$ and in $\text{g/dm}^3$ .

[ $M_r(\text{CH}_3\text{COOH}) = 60$ ]

Example 6ExtendedTitration calculation with a 1 : 2 mole ratio; concentration in mol/dm³ and g/dm³[5 marks]

Sodium carbonate and hydrochloric acid: a 1 : 2 ratio

$25.0\text{ cm}^3$ of aqueous sodium carbonate needs $23.40\text{ cm}^3$ of $0.150\text{ mol/dm}^3$ hydrochloric acid for neutralisation.

$\text{Na}_2\text{CO}_3\text{(aq)} + 2\text{HCl(aq)} \rightarrow 2\text{NaCl(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)}$

Calculate the concentration of the sodium carbonate in

(a) $\text{mol/dm}^3$ and

(b) $\text{g/dm}^3$ .

[ $A_r$ : C $= 12$ , O $= 16$ , Na $= 23$ ]

Example 7ExtendedMultiple choice: titration volume with a 1 : 2 ratio[1 mark]

Multiple choice: volume of acid for calcium hydroxide

$25.0\text{ cm}^3$ of $0.0200\text{ mol/dm}^3$ calcium hydroxide is neutralised by $0.0500\text{ mol/dm}^3$ hydrochloric acid.

$\text{Ca(OH)}_2\text{(aq)} + 2\text{HCl(aq)} \rightarrow \text{CaCl}_2\text{(aq)} + 2\text{H}_2\text{O(l)}$

What volume of hydrochloric acid is needed?

A $5.0\text{ cm}^3$

B $10.0\text{ cm}^3$

C $20.0\text{ cm}^3$

D $40.0\text{ cm}^3$

Example 8ExtendedDescribe preparing a soluble salt from an acid and alkali by titration then crystallisation; theoretical mass[6 marks]

Making a pure salt by titration

Potassium nitrate can be made from aqueous potassium hydroxide and dilute nitric acid.

(a) Name the method used to find the exact volume of acid that neutralises $25.0\text{ cm}^3$ of the alkali.

(b) Describe how the student then obtains pure, dry crystals of potassium nitrate that contain no indicator.

(c) The potassium hydroxide was $1.00\text{ mol/dm}^3$ . Calculate the maximum mass of potassium nitrate that can be made from $25.0\text{ cm}^3$ .

[ $A_r$ : N $= 14$ , O $= 16$ , K $= 39$ ]

Example 9ExtendedExplain the effect of rinsing, water in the flask, warming and burette capacity on the titre[6 marks]

How errors in technique change the titre

A student titrates $25.0\text{ cm}^3$ of aqueous sodium hydroxide (in the flask) with dilute hydrochloric acid (in a $50\text{ cm}^3$ burette). The correct titre is $27.30\text{ cm}^3$ . State and explain the effect, if any, on the titre of each of these.

(a) The burette was rinsed with distilled water but not with the acid before filling.

(b) The conical flask was wet with distilled water before the alkali was added.

(c) The alkali was warmed to $30\,^{\circ}\text{C}$ before the titration.

(d) The student wants to use $50.0\text{ cm}^3$ of alkali instead. Explain why this would not work with the same burette.

Example 10ExtendedUse titres to compare concentrations qualitatively and quantitatively[4 marks]

Comparing the concentrations of two alkalis

Two sodium hydroxide solutions, P and Q, are each titrated against $25.0\text{ cm}^3$ portions of the same $0.100\text{ mol/dm}^3$ hydrochloric acid (in the flask).

solution	mean titre / $\text{cm}^3$
P	$12.40$
Q	$24.80$

(a) Which solution is more concentrated? Explain, using the data.

(b) Calculate the concentration of P.

Example 11ChallengeScale moles from an aliquot to the whole solution; find Mr; deduce the water of crystallisation[6 marks]

Water of crystallisation in washing soda by titration

$2.86$ g of hydrated sodium carbonate, $\text{Na}_2\text{CO}_3 \cdot x\text{H}_2\text{O}$ , is dissolved in distilled water and made up to $250\text{ cm}^3$ . A $25.0\text{ cm}^3$ portion needs $20.00\text{ cm}^3$ of $0.100\text{ mol/dm}^3$ hydrochloric acid.

$\text{Na}_2\text{CO}_3 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{H}_2\text{O} + \text{CO}_2$

Calculate the value of $x$ .

[ $A_r$ : H $= 1$ , C $= 12$ , O $= 16$ , Na $= 23$ ]

Example 12ChallengeTitre from readings; 2 : 1 ratio with sulfuric acid; scale up; percentage purity[6 marks]

Percentage purity of potassium hydroxide

$2.00$ g of impure potassium hydroxide is dissolved and made up to $250\text{ cm}^3$ . A $25.0\text{ cm}^3$ portion is titrated with $0.100\text{ mol/dm}^3$ sulfuric acid. The burette readings are shown.

$2\text{KOH(aq)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{K}_2\text{SO}_4\text{(aq)} + 2\text{H}_2\text{O(l)}$

Calculate the percentage purity of the potassium hydroxide. Assume the impurities do not react with acid.

[ $A_r$ : H $= 1$ , O $= 16$ , K $= 39$ ]

These worked examples are written by Tutopiya to cover the same syllabus content as the official Cambridge IGCSE 0620 specification (2026-2028). They are exam-style questions, not reproductions of past paper questions.

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The Periodic Table

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Chemistry of the Environment

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Acid–Base Titrations Worked ExamplesIGCSE Chemistry 0620

Example 1CoreName titration apparatus; describe how the alkali is measured; choose an indicator and identify the end-point[6 marks]

Describing a titration: apparatus, indicator and end-point

The diagram shows apparatus used to titrate aqueous sodium hydroxide with dilute hydrochloric acid, using methyl orange indicator.

(a) Name P, Q and R.

(b) Name the apparatus used to put exactly $25.0\text{ cm}^3$ of the alkali into Q.

(c) Describe how the student adds the acid and how the end-point is identified.

(d) Give one reason why universal indicator is not used.

Example 2CoreMultiple choice: indicator and colour change at the end-point[1 mark]

Multiple choice: thymolphthalein colours in a titration

Aqueous potassium hydroxide is placed in a conical flask with a few drops of indicator. Dilute nitric acid is added from a burette until the end-point.

Which row is correct?

	indicator	colour at the start	colour at the end-point
A	thymolphthalein	colourless	blue
B	thymolphthalein	blue	colourless
C	universal indicator	purple	green
D	methyl orange	red	yellow

Example 3ExtendedRead burette scales to 0.05 cm³; record to 2 d.p.; subtract; select concordant results and average[5 marks]

Reading burettes and choosing concordant titres

The diagram shows the burette readings at the start and end of three accurate titrations.

(a) Record the initial and final readings and the titre for each run.

(b) Titres within $0.10\text{ cm}^3$ of each other are concordant. Calculate the mean titre to use in calculations.

Example 4ExtendedIdentify the end-point colour; purpose of white tile, swirling and dropwise addition[5 marks]

Methyl orange end-point and good titration technique

A student titrates aqueous sodium carbonate in a conical flask with dilute hydrochloric acid, using methyl orange. The diagram shows the colour of the flask at three stages.

(a) Which flask shows

(i) the start and

(ii) the end-point? Explain what flask 3 shows.

(b) State the purpose of the white tile.

(c) State what the student should do to the flask while adding the acid.

(d) Explain why the acid is added drop by drop near the end-point.

Example 5ExtendedTitre from burette readings; 1 : 1 calculation; dilution factor; convert mol/dm³ to g/dm³[6 marks]

Concentration of ethanoic acid in vinegar

$\text{CH}_3\text{COOH(aq)} + \text{NaOH(aq)} \rightarrow \text{CH}_3\text{COONa(aq)} + \text{H}_2\text{O(l)}$

(a) Find the volume of sodium hydroxide used.

(b) Calculate the concentration of ethanoic acid in the diluted vinegar.

(c) Calculate the concentration of ethanoic acid in the original vinegar in $\text{mol/dm}^3$ and in $\text{g/dm}^3$ .

[ $M_r(\text{CH}_3\text{COOH}) = 60$ ]

Example 6ExtendedTitration calculation with a 1 : 2 mole ratio; concentration in mol/dm³ and g/dm³[5 marks]

Sodium carbonate and hydrochloric acid: a 1 : 2 ratio

$25.0\text{ cm}^3$ of aqueous sodium carbonate needs $23.40\text{ cm}^3$ of $0.150\text{ mol/dm}^3$ hydrochloric acid for neutralisation.

$\text{Na}_2\text{CO}_3\text{(aq)} + 2\text{HCl(aq)} \rightarrow 2\text{NaCl(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)}$

Calculate the concentration of the sodium carbonate in

(a) $\text{mol/dm}^3$ and

(b) $\text{g/dm}^3$ .

[ $A_r$ : C $= 12$ , O $= 16$ , Na $= 23$ ]

Example 7ExtendedMultiple choice: titration volume with a 1 : 2 ratio[1 mark]

Multiple choice: volume of acid for calcium hydroxide

$25.0\text{ cm}^3$ of $0.0200\text{ mol/dm}^3$ calcium hydroxide is neutralised by $0.0500\text{ mol/dm}^3$ hydrochloric acid.

$\text{Ca(OH)}_2\text{(aq)} + 2\text{HCl(aq)} \rightarrow \text{CaCl}_2\text{(aq)} + 2\text{H}_2\text{O(l)}$

What volume of hydrochloric acid is needed?

A $5.0\text{ cm}^3$

B $10.0\text{ cm}^3$

C $20.0\text{ cm}^3$

D $40.0\text{ cm}^3$

Example 8ExtendedDescribe preparing a soluble salt from an acid and alkali by titration then crystallisation; theoretical mass[6 marks]

Making a pure salt by titration

Potassium nitrate can be made from aqueous potassium hydroxide and dilute nitric acid.

(a) Name the method used to find the exact volume of acid that neutralises $25.0\text{ cm}^3$ of the alkali.

(b) Describe how the student then obtains pure, dry crystals of potassium nitrate that contain no indicator.

(c) The potassium hydroxide was $1.00\text{ mol/dm}^3$ . Calculate the maximum mass of potassium nitrate that can be made from $25.0\text{ cm}^3$ .

[ $A_r$ : N $= 14$ , O $= 16$ , K $= 39$ ]

Example 9ExtendedExplain the effect of rinsing, water in the flask, warming and burette capacity on the titre[6 marks]

How errors in technique change the titre

(a) The burette was rinsed with distilled water but not with the acid before filling.

(b) The conical flask was wet with distilled water before the alkali was added.

(c) The alkali was warmed to $30\,^{\circ}\text{C}$ before the titration.

(d) The student wants to use $50.0\text{ cm}^3$ of alkali instead. Explain why this would not work with the same burette.

Example 10ExtendedUse titres to compare concentrations qualitatively and quantitatively[4 marks]

Comparing the concentrations of two alkalis

Two sodium hydroxide solutions, P and Q, are each titrated against $25.0\text{ cm}^3$ portions of the same $0.100\text{ mol/dm}^3$ hydrochloric acid (in the flask).

solution	mean titre / $\text{cm}^3$
P	$12.40$
Q	$24.80$

(a) Which solution is more concentrated? Explain, using the data.

(b) Calculate the concentration of P.

Example 11ChallengeScale moles from an aliquot to the whole solution; find Mr; deduce the water of crystallisation[6 marks]

Water of crystallisation in washing soda by titration

$\text{Na}_2\text{CO}_3 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{H}_2\text{O} + \text{CO}_2$

Calculate the value of $x$ .

[ $A_r$ : H $= 1$ , C $= 12$ , O $= 16$ , Na $= 23$ ]

Example 12ChallengeTitre from readings; 2 : 1 ratio with sulfuric acid; scale up; percentage purity[6 marks]

Percentage purity of potassium hydroxide

$2\text{KOH(aq)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{K}_2\text{SO}_4\text{(aq)} + 2\text{H}_2\text{O(l)}$

Calculate the percentage purity of the potassium hydroxide. Assume the impurities do not react with acid.

[ $A_r$ : H $= 1$ , O $= 16$ , K $= 39$ ]

Acid–Base Titrations Worked ExamplesIGCSE Chemistry 0620

Describing a titration: apparatus, indicator and end-point

Multiple choice: thymolphthalein colours in a titration

Reading burettes and choosing concordant titres

Methyl orange end-point and good titration technique

Concentration of ethanoic acid in vinegar

Sodium carbonate and hydrochloric acid: a 1 : 2 ratio

Multiple choice: volume of acid for calcium hydroxide

Making a pure salt by titration

How errors in technique change the titre

Comparing the concentrations of two alkalis

Water of crystallisation in washing soda by titration

Percentage purity of potassium hydroxide

More IGCSE Chemistry 0620 worked examples

Experimental Techniques and Chemical Analysis

States of Matter

Atoms, Elements and Compounds

Stoichiometry

Electrochemistry

Chemical Energetics

Chemical Reactions

Acids, Bases and Salts

The Periodic Table

Metals

Chemistry of the Environment

Organic Chemistry

Alternative to Practical

Acid–Base Titrations Worked ExamplesIGCSE Chemistry 0620

Describing a titration: apparatus, indicator and end-point

Multiple choice: thymolphthalein colours in a titration

Reading burettes and choosing concordant titres

Methyl orange end-point and good titration technique

Concentration of ethanoic acid in vinegar

Sodium carbonate and hydrochloric acid: a 1 : 2 ratio

Multiple choice: volume of acid for calcium hydroxide

Making a pure salt by titration

How errors in technique change the titre

Comparing the concentrations of two alkalis

Water of crystallisation in washing soda by titration

Percentage purity of potassium hydroxide

More IGCSE Chemistry 0620 worked examples

Experimental Techniques and Chemical Analysis

States of Matter

Atoms, Elements and Compounds

Stoichiometry

Electrochemistry

Chemical Energetics

Chemical Reactions

Acids, Bases and Salts

The Periodic Table

Metals

Chemistry of the Environment

Organic Chemistry

Alternative to Practical