chapter 8 - acid and bases (part three ; indicators)

Question 1

definition of indicators

Answer 1

coloured dyes that change in colour when added to an acid or alkali

Question 2

name 5 indicators

Answer 2

[SLUMT]

1. screened methyl orange
2. litmus
3. universal indicator
4. methyl orange
5. thymolphthalein

Question 3

state the colours of methyl orange in acidic and alkaline solution

state the pH range at which it changes colour

Answer 3

in acidic : red
in alkali : yellow

pH which it changes colour: 3-5

Question 4

state the colours of screened methyl orange in acidic and alkaline solution

state the pH range at which it changes colour

Answer 4

in acidic : violet
in alkali : green

pH which it changes colour: 3-5

Question 5

state the colours of litmus in acidic and alkaline solution

state the pH range at which it changes colour

Answer 5

in acidic : red
in alkali : blue

pH which it changes colour: 5-8

Question 6

state the colours of thymolphthalein in acidic and alkaline solution

state the pH range at which it changes colour

Answer 6

in acidic : colourless
in alkali : blue

pH which it changes colour: 9-10.5

Question 7

what is slaked lime?

Answer 7

calcium hydroxide

it is a base that reacts with acids in the soil and raises pH so that plants can grow healthily

however, adding too much will make the soil too alkaline and unsuitable for plant growth