Required Practical 07: Identifying Ions

Question 1

Question:

Compound A produced a lilac flame test. A sample of compound A was reacted with silver nitrate solution and dilute nitric acid. A yellow precipitate was formed.

Identify compound A.

Answer 1

Lilac flame: potassium ion
Yellow precipitate: iodide ion

Compound A = potassium iodide

Question 2

Question:

Compound C produced an orange-red flame test. A sample of compound C effervesced when tested with hydrochloric acid and the gas produced turned limewater cloudy.

Identify compound C.

Answer 2

Orange-red flame: calcium ion
Cloudy limewater: carbonate ions present

Compound C = calcium carbonate

Question 3

Question:

Compound B was reacted with sodium hydroxide solution and produced a blue precipitate. Compound C was then reacted with barium chloride solution and dilute hydrochloric acid. This reaction produced a white precipitate.

Identify compound C.

Answer 3

Blue precipitate: copper (II) ion
White precipitate: sulfate ion

Compound C = copper (II) sulfate