12.2 Acid- Base titrations | Cambridge O Level Chemistry Topic Questions 2023

1a2 marks

A student does three titrations with dilute hydrochloric acid and potassium hydroxide solution.

Complete the equation to show the products formed during this reaction.

potassium hydroxide + hydrochloric acid → potassium ______ + _______

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1b1 mark

Some of the apparatus the student uses is shown below.

17a

Name the piece of equipment the student will use to measure out the 25.0 cm³ of potassium hydroxide solution.

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1c1 mark

In her first titration the student measures the initial volume of hydrochloric acid in the burette.

She slowly adds the acid until the potassium hydroxide is just neutralised.

She then measures the volume of the hydrochloric acid again.

Describe how she can tell when the potassium hydroxide solution is just neutralised.

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1d2 marks

Look at the diagrams. They show parts of the burette during the first titration.

q17c-paper-2-specimen-2016-ocr-gcse-chem

Here is the student’s results table.

Titration number	1	2	3
final reading in cm³		37.5	32.1
initial reading in cm³		20.4	15.0
titre (volume of acid added) in cm³		17.1	17.1

Complete the table by recording the burette readings from the diagrams.

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16 marks

The diagram shows two bottles of liquid oven cleaner.

oven-cleaner

The oven cleaners contain sodium hydroxide solution. Plan an investigation to show which oven cleaner contains the highest concentration of sodium hydroxide.

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2a2 marks

A student investigated the reaction between aqueous sodium hydroxide and acid K.
Two experiments were carried out.

Experiment 1

Using a measuring cylinder, 25 cm³ of acid K was poured into a conical flask.
Phenolphthalein indicator was added to the flask. A burette was filled with aqueous sodium hydroxide to the 0.0 cm³ mark. Aqueous sodium hydroxide was added from the burette to the flask and the mixture shaken until the solution showed a permanent colour change.
The final volume was measured. Use the burette diagram to record the final volume in the table and complete the table.

12-1-q11a

	burette readings
final volume / cm³
initial volume / cm³
difference / cm³

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2b2 marks

Experiment 2
The solution was poured away and the conical flask rinsed.
Using a measuring cylinder, 50 cm³of acid K was poured into the conical flask. 0.3 g of powdered calcium carbonate was added to the flask and the flask shaken until no further reaction was observed.
Phenolphthalein was added to the mixture in the flask.
A burette was filled with the same aqueous sodium hydroxide and the initial volume measured. Aqueous sodium hydroxide was added from the burette to the flask and the mixture shaken until the solution showed a permanent colour change.
Use the burette diagrams to record the initial and final volumes in the table and complete the table.

12-1-q11b

	burette readings
final volume / cm³
initial volume / cm³
difference / cm³

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2c1 mark

What type of chemical reaction occurred when acid K reacted with sodium hydroxide?

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2d1 mark

If Experiment 1 were repeated using 50 cm³ of acid K, what volume of sodium hydroxide would be required to change the colour of the indicator?

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2e

5 marks

i)

What were the effects of adding 0.3 g of powdered calcium carbonate to acid K?

[2]

ii)

Use your answer in (d) to work out the difference between the volume of sodium hydroxide needed to completely react with 50 cm³ of acid K and the volume of sodium hydroxide used in Experiment 2.

[2]

iii)

Estimate the mass of calcium carbonate that would be needed to be added to 50 cm³ of acid K to require 0.0 cm³ of sodium hydroxide.

[1]

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2f2 marks

What would be the effect on the results if the solutions of acid K were warmed before adding the sodium hydroxide? Give a reason for your answer.

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2g4 marks

Separate: Chemistry Only

Suggest the advantage, if any, of

i)

using a pipette to measure the volume of acid K.

[2]

ii)

using a polystyrene cup instead of a flask.

[2]

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1a1 mark

The following paragraph was taken from a student’s notebook.

To make potassium chloride

25.0 cm³ of aqueous potassium hydroxide were placed in a flask and a few drops of indicator were added. Dilute hydrochloric acid was added to the flask until the indicator changed colour. The volume of acid used was 19.0 cm³.

What piece of apparatus should be used to measure the aqueous potassium hydroxide?

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1b3 marks

i)

Name a suitable indicator that could be used.

[1]

ii)

The indicator would change from ........................... to ................................

[2]

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1c2 marks

Which solution was more concentrated? Explain your answer.

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1d3 marks

How could pure crystals of potassium chloride be obtained from this experiment?

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2a2 marks

A student investigated the reaction between two different solutions of dilute hydrochloric acid, A and B, and solution C which is alkaline.

Two experiments were carried out

Experiment 1

A burette was filled with solution A of dilute hydrochloric acid to the 0.0 cm³ mark. Using a measuring cylinder, 20 cm³ of solution C was poured into a conical flask. A few drops of methyl orange were added to the flask.

Solution A was added to the flask, with shaking, until the mixture just changed colour. Use the burette diagram to record the burette reading in the table and complete the table.

XwZN6J_N_12-1-q9a

	burette readings
final volume / cm³
initial volume / cm³
difference / cm³

How did you do?

2b2 marks

Experiment 2

The burette was emptied and rinsed, first with distilled water, and then with a little of solution B. The burette was filled with solution B of dilute hydrochloric acid to the 0.0 cm³ mark.

Experiment 1 was repeated using solution B.

Use the burette diagram to record the burette reading in the table and complete the table.

12-1-q9b

	burette readings
final volume / cm³
initial volume / cm³
difference / cm³

How did you do?

2c2 marks

i)

What type of chemical reaction takes place when hydrochloric acid reacts with alkaline solutions?

[1]

ii)

Why is methyl orange added to the flask?

[1]

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2d2 marks

Why was the burette rinsed, first with distilled water and then with solution B, before starting Experiment 2?

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2e4 marks

Separate: Chemistry and Extended Only

i)

In which experiment was the greater volume of dilute hydrochloric acid used?

[1]

ii)

Compare the volumes of dilute hydrochloric acid used in Experiments 1 and 2.

[1]

iii)

Suggest, in terms of the concentration of solutions A and B, an explanation for the difference in volumes used.

[2]

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2f2 marks

Separate: Chemistry and Extended Only

If Experiment 2 was repeated using 10 cm³of solution C, what volume of dilute hydrochloric acid would be used? Explain your answer.

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2g2 marks

Separate: Chemistry Only

Give one advantage and one disadvantage of using a measuring cylinder for solution C.

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2h4 marks

Describe a method other than titration, using a different reactant, that could be used to compare the concentrations of the two solutions of dilute hydrochloric acid, A and B.

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Easy
Medium
Hard

A	Add a few drops of phenolphthalein
B	Add the HCl slowly until the endpoint is reached
C	Add HCl into the burette and record initial volume
D	Pipette 25 cm³ of NaOH into a conical flask
E	Record the volume of acid added

Red to yellow

Pink to colourless

Colourless to pink

Yellow to red

first step								last step
C

Acid- Base titrations (Cambridge O Level Chemistry)

Topic Questions

Separate: Chemistry Only

Separate: Chemistry and Extended Only

Separate: Chemistry and Extended Only

Separate: Chemistry Only