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Edexcel IGCSE Chemistry acids, alkalis and titrations

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

Syllabus
First assessment 2019
Course
Chemistry 4CH1

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 indicators2.29 The pH scale2.30 Universal indicator2.31 Acids and alkalis in water2.32 Neutralisation2.33C Carry out an acid-alkali titration

(f) Acids, alkalis and titrations question 1

[Maximum number: 3]

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

Question (a)

(a)

Identify the ion that makes the sodium hydroxide solution alkaline.

[ 1 ]

Question (b)

(b)

What is a possible pH of ammonia solution?

A

3

B

6

C

11

D

14

[ 1 ]

Question (c)

(c)

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

[ 1 ]

Question (i)

(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

colourless

pink

[ 1 ]

(f) Acids, alkalis and titrations question 2

[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.

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