Testing for ions

Question 1

Ammonium (NH₄⁺)

Answer 1

Test:
1. Warm sample with sodium hydroxide solution
2. Test the gas produced with moist red litmus paper
Results:
- Pungent-smelling gas
- Red litmus paper turns blue
- White fumes of ammonium chloride

Question 2

Magnesium (Mg²⁺)

Answer 2

Test:
1. Make a solution of the compound
2. Add a few drops of sodium hydroxide solution
Results:
- White precipitate

Question 3

Calcium (Ca²⁺)

Answer 3

Test:
1. Dip a nichrome wire into concentrated hydrochloric acid and then into the sample
2. Place in a blue Bunsen flame
Results:
- Brick-red flame

Question 4

Barium (Ba²⁺)

Answer 4

Test:
1. Dip a nichrome wire into concentrated hydrochloric acid and then into the sample
2. Place in a blue Bunsen flame
Results:
- Green flame

Question 5

Strontium (Sr²⁺)

Answer 5

Test:
1. Dip a nichrome wire into concentrated hydrochloric acid and then into the sample
2. Place in a blue Bunsen flame
Results:
- Red flame

Question 6

Chloride (Cl⁻)

Answer 6

Test:
1. Make a solution of the compound
2. Add acidified silver nitrate solution followed by aqueous ammonia
Results:
- White precipitate (Which dissolves in dilute aqueous ammonia to give a colourless solution)

Question 7

Bromide (Br⁻)

Answer 7

Test:
1. Make a solution of the compound
2. Add acidified silver nitrate solution followed by aqueous ammonia
Results:
- Cream precipitate (Insoluble in dilute aqueous ammonia, dissolves in concentrated aqueous ammonia to give a colourless solution)

Question 8

Iodide (I⁻)

Answer 8

Test:
1. Make a solution of the compound
2. Add acidified silver nitrate solution followed by aqueous ammonia
Results:
- Yellow precipitate (Insoluble in both dilute and concentrate aqueous ammonia)

Question 9

Sulfate (SO₄²⁻)

Answer 9

Test:
1. Make a solution of the compound
2. Add acidified barium chloride solution
Results:
- White precipitate

Question 10

Hydroxide (OH⁻)

Answer 10

Test:
1. Warm with solid ammonium salt
2. Test the gas produced with red litmus paper
Results:
- Pungent gas (ammonia)
- Red litmus paper turns blue
- Adding concentrated HCl will produce white fumes

Question 11

Carbonate (CO₃²⁻)

Answer 11

Test:
1. Add dilute nitric acid 
2. Test the gas produced with limewater
Results:
- Effervescence
- Gas changes colourless limewater milky