C1.4.2 Indicators and pH

Question 1

What is an indicator?

Answer 1

Something that tells us if a substance is an acid or alkali.

Question 2

How do indicators work?

Answer 2

They contain a dye which changes colour in acidic and alkaline conditions.

Question 3

You add blue litmus paper to an unknown solution and it turns red.

You add red litmus paper to an unknown solution and it stays red.

The substance is…

Answer 3

Acidic

Question 4

You add red litmus paper to an unknown solution and it turns blue.

You add blue litmus paper to an unknown solution and it stays blue.

The substance is…

Answer 4

Alkaline

Question 5

You add blue litmus paper to an unknown solution and it stays blue.

You add red litmus paper to an unknown solution and it stays red.

The substance is…

Answer 5

Neutral

Question 6

If you want to know exactly how acidic or alkaline a substance is then we use…

Answer 6

Universal Indicator

Question 7

Describe a solution that turns universal indicators the following colours:

Answer 7

Question 8

Describe a solution that turns universal indicators the following colours:

Answer 8

Question 9

Describe a solution that turns universal indicators the following colours:

Answer 9

Question 10

Describe a solution that turns universal indicators the following colours:

Answer 10

Question 11

Describe a solution that turns universal indicators the following colours:

Answer 11

Question 12

pH1 =

Answer 12

Strong acid

Question 13

pH2 =

Answer 13

Strong acid

Question 14

pH3=

Answer 14

Strong acid

Question 15

pH4 =

Answer 15

Weak acid

Question 16

pH5=

Answer 16

Weak acid

Question 17

pH6=

Answer 17

Weak acid

Question 18

pH7=

Answer 18

Neutral

Question 19

pH8=

Answer 19

Weak alkali

Question 20

pH9=

Answer 20

Weak alkali

Question 21

pH10=

Answer 21

Weak alkali

Question 22

pH11=

Answer 22

Strong alkali

Question 23

pH12=

Answer 23

Strong alkali

Question 24

pH13 =

Answer 24

Strong alkali

Question 25

pH14=

Answer 25

Strong alkali

Question 26

Give an example of useful n eutralisation reactions.

Answer 26

Toothpaste is alkaline to neutralise the acids produced by bacteria that cause acid erosion.

Indigestion tablets neutralised stomach acids to prevent heartburn/indigestion.