Tests for Ions

Question 1

What colour flames do calcium, strontium and barium ions produce?

Answer 1

• Ca2+ brick-red
• Sr2+ red
• Ba2+ green

Question 2

How can you test for ammonium ions?

Answer 2

• Damp red litmus paper because ammonia gas is alkaline
• Litmus paper needs to be damp so ammonia gas can dissolve
• Add hydroxide ions to a solution containing ammonium ions and warm, ammonia gas and water will be produced
• Red litmus will turn blue

Question 3

How can you test for hydroxide ions?

Answer 3

Hydroxide ions made solutions alkaline, so you can use a pH indicator. If you dip a piece of red litmus, it will turn blue

Question 4

How can you test for carbonate ions?

Answer 4

Add an acid e.g. dilute HCl.
Carbonate ions will react with hydrogen ions to produce carbon dioxide and water.
There will be fizzing from the CO2

Question 5

How can you test for carbon dioxide?

Answer 5

Bubble the gas through limewater. Limewater will go cloudy