Ion tests

Question 1

What equipment do you use to carry out a flame test

Answer 1

Wire loop cleaned in HCl (to hold the sample) - platinum wire as it is unreactive and has a high melting point
Bunsen burner etc…

Question 2

Name the coloured flames produced during the flame test of these cations:
Lithium
Sodium
Potassium
Calcium
Copper

Answer 2

Lithium - red
Sodium - yellow
Potassium - lilac
Calcium - orange/red
Copper - blue/green

Question 3

What test would you carry out to determine dissolved metal ions?

Answer 3

Precipitation reactions involving sodium hydroxide solution, different metal ions produce different coloured hydroxide precipitates

Question 4

Name the coloured precipitate formed from the different metal ions:
Iron (II)
Iron (III)
Copper
Calcium
Aluminium

Answer 4

Iron (II) - green
Iron (III) - brown
Copper - blue
Calcium - white
Aluminium - white

Question 5

Describe the test for ammonium

Answer 5

Changes the colour of damp red litmus paper to blue

Question 6

Describe the test for carbonate ions

Answer 6

• Add dilute HCl
• Production of CO2 causes bubbling
• Carry out another test to check that the gas produced is CO2 e.g. will turn limewater milky

Question 7

Describe the test for sulfate ions

Answer 7

• Add dilute HCl
• Add barium chloride
• White precipitate of barium sulfate forms if the sample contains sulfate ions

Question 8

Describe the test for Halide ions

Answer 8

• Add dilute nitric acid
• Add a few drops of silver nitrate solution
• Different coloured silver halide precipitates form , depending on the halide present

Question 9

Why do you add dilute HCl/dilute nitric acid when testing for sulfate/halide ions?

Answer 9

• Acidifies the solution, removing carbonate ions that might give a precipitate to the test

Question 10

Name the coloured precipitate formed from the different halide ions:
Chloride
Iodide
Bromide

Answer 10

Chloride - White
Iodide - Cream
Bromide - Yellow