Paper 1 - Acids, bases and salt preparations

Question 1

Describe the use of litmus paper to distinguish between acidic and alkaline solutions

Answer 1

• Litmus paper tests whether a solution is acidic or alkaline because it changes colour at about pH7.
• It is red in acidic solutions, purple in neutral solutions and blue in alkaline solutions

Question 2

Describe the use of phenolphthalein to distinguish between acidic and alkaline solutions

Answer 2

Phenolphthalein will change from colourless in acidic solutions to bright pink in alkaline solutions

Question 3

Describe the use of methyl orange to distinguish between acidic and alkaline solutions

Answer 3

Methyl orange changes from red in acidic solutions to yellow in alkaline solutions

Question 4

What are the pH values for strongly acidic?

Answer 4

0-3

Question 5

What are the pH values for weakly acidic?

Answer 5

4-6

Question 6

What is the pH value for neutral?

Answer 6

7

Question 7

What are the pH values for weakly alkaline?

Answer 7

8-10

Question 8

What are the pH values for strongly alkaline?

Answer 8

11-14

Question 9

Describe the use of universal indicator to measure the approximate pH value of an
aqueous solution

Answer 9

The universal indicator contains a useful combination of dyes that will give off different colours for different pH values

Question 10

What colour is universal indicator for a strong acid?

Answer 10

Red

Question 11

What colour is universal indicator for a weak acid?

Answer 11

Orange-Yellow

Question 12

What colour is universal indicator for a netral solution?

Answer 12

Green

Question 13

What colour is universal indicator for a weak alkali?

Answer 13

Blue

Question 14

What colour is universal indicator for a strong alkali?

Answer 14

Indigo

Question 15

Describe acids in terms of ions

Answer 15

Acids are a source of H+ions

Question 16

Describe alkalis in terms of ions

Answer 16

Alkalis are a source of OH- ions

Question 17

What can alkalis do to acids?

Answer 17

Neutralise them