Edexcel IGCSE Chemistry F Acids Alkalis and Titrations Questions

Practise acids-and-titrations questions by interpreting indicator colours, pH values, endpoints and accurate titre tables.

Exam points

Link indicator colours and pH ranges to acidic, neutral or alkaline solutions.
Choose titration indicators and endpoint colours from tables or named acid-alkali reactions.
Explain accuracy improvements such as rinsing apparatus or using concordant titres.

Covered syllabus points

2.28 Acid–base indicators 2.29 The pH scale 2.30 Universal indicator 2.31 Acids and alkalis in water 2.32 Neutralisation 2.33C Carry out an acid-alkali titration

[Maximum number: 3]

Sodium hydroxide dissolves in water, forming a strongly alkaline solution.
Ammonia dissolves in water, forming a slightly less alkaline solution.

(a)

Identify the ion that makes the sodium hydroxide solution alkaline.

[ 1 ]

hydroxide/ $\mathrm{OH}^{-}$

ALLOW HO ${ }^{-}$

REJECT OH

grad

(b)

What is a possible pH of ammonia solution?

[ 1 ]

(c)

When ammonia solution reacts with sulfuric acid, a neutralisation reaction occurs and ammonium sulfate forms.

[ 1 ]

(i)

The diagram shows a beaker containing some ammonia solution and a few drops of phenolphthalein indicator.

Dilute sulfuric acid is added to the beaker until it is in excess.

What are the colours of the phenolphthalein indicator before and after adding excess sulfuric acid?

Figure for Question (i) — Edexcel IGCSE Chemistry

Before

After

orange

red

yellow

red

pink

colourless

pink

[ 1 ]

[Maximum number: 2]

A teacher adds a small piece of lithium to water and collects the gas produced.

The teacher adds a few drops of universal indicator to the solution at the end of the reaction.

Explain the final colour of the universal indicator.

[Maximum number: 1]

This question is about salts.

Soluble salts can be prepared by the reaction between a metal oxide and an acid.

The equation for this type of reaction is

metal oxide + acid → salt + water

State the name given to this type of reaction.

[Maximum number: 1]

Sodium hydroxide dissolves in water, forming a strongly alkaline solution.
Ammonia dissolves in water, forming a slightly less alkaline solution.

When ammonia solution reacts with sulfuric acid, a neutralisation reaction occurs and ammonium sulfate forms.

Figure for Question 4 — Edexcel IGCSE Chemistry

Before

After

orange

red

yellow

red

pink

colourless

pink

[Maximum number: 1]

Sodium hydroxide dissolves in water, forming a strongly alkaline solution.
Ammonia dissolves in water, forming a slightly less alkaline solution.

What is a possible pH of ammonia solution?

[Maximum number: 1]

Sodium hydroxide dissolves in water, forming a strongly alkaline solution.
Ammonia dissolves in water, forming a slightly less alkaline solution.

Identify the ion that makes the sodium hydroxide solution alkaline.

hydroxide/ $\mathrm{OH}^{-}$

ALLOW HO ${ }^{-}$

REJECT OH

grad

[Maximum number: 6]

Sodium sulfate can be prepared by the reaction between sodium hydroxide solution and sodium hydrogensulfate ( $\mathrm{NaHSO}_{4}$ ) solution.

This is the equation for the reaction.

\mathrm{NaOH}(\mathrm{aq})+\mathrm{NaHSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Sodium hydrogensulfate solution is acidic.
A student adds $25.0 \mathrm{~cm}^{3}$ of sodium hydroxide solution to a conical flask and adds two drops of indicator.

The student does a titration.

(a)

Name a piece of apparatus that should be used to add $25.0 \mathrm{~cm}^{3}$ of sodium hydroxide solution to the conical flask.

[ 1 ]

(b)

Describe the method the student should use to find the accurate volume of sodium hydrogensulfate solution needed to neutralise the 25.0 cm3 of sodium hydroxide solution.

[ 5 ]

All question bank results loaded

Covered syllabus points

Question 1

Question (a)

Question (b)

Question (c)

Question (i)

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question (a)

Question (b)