C12 - Chemical Analysis

Question 1

mnumonic device to remember metal ions and their colours in a flame

Answer 1

Lions Chase Small Cats / Kittens

it is written in ‘rainbow’ order (red to lilac)

Question 2

list:

colour of positive metal ions in a flame

5 examples

Answer 2

• Lithium - crimson
• Calcium - orange-red
• Sodium - yellow
• Copper - green
• Potassium - lilac

Question 3

list:

metal ions which make white precipitates and if they dissolve or not

sodium hydroxide test, 3 examples

Answer 3

• Aluminium - dissolves in excess sodium hydroxide solution
• Calcium - no change in excess sodium hydroxide solution
• Magnesium - no change in excess sodium hydroxide solution

Question 4

list:

metal ions which make non-white precipitates

sodium hydroxide test

Answer 4

• Copper - blue
• Iron (ii) - green
• Iron (iii) - brown

Question 5

what two tests can be performed on cations

metal ions

Answer 5

• flame tests
• sodium hydroxide precipitate tests

Question 6

define:

cation

Answer 6

positively charged particle

Question 7

define:

anion

Answer 7

negatively charged particle

Question 8

describe:

test for carbonate ions

CO₃ ^2-

Answer 8

1. Add a few drops of dilute hydrochloric acid
2. Bubbles are produced if carbonate ions are present
3. Confirm that the gas is carbon dioxide - limewater turns milky/cloudy.

Question 9

describe:

test for sulfate ions

SO₄ ^2-

Answer 9

1. Add a few drops of dilute hydrochloric acid
2. Add a few drops of barium chloride solution
3. A white precipitate forms if sulfate ions are present.

Question 10

describe:

test for halide ions

Answer 10

1. Add a few drops of dilute nitric acid
2. few drops of silver nitrate solution
3. observe the colour of any precipitate formed

Question 11

list:

colour of precipitate from halide ions

Answer 11

• Chloride - white
• Bromide - cream
• Iodide - yellow