Chemistry-Test for ions

Test for Anions(-) and aqueous Cations(+)

Carbonate, CO₃^2- 

Test

1. Add dilute acid

2. Test for carbon dioxide gas with limewater

Result:

Effervescence, Carbon dioxide produced

Chloride, Cl^- (In solution)

Test

1. Acidify with dilute nitric acid

2. Then add aqueous silver nitrate

Result: White precipitate (ppt)

Bromide, Br^- (In solution)

Test

1. Acidify with dilute nitric acid

2. Then add aqueous silver nitrate

Result: Cream ppt

Iodide, I^- (In solution)

Test

1. Acidify with dilute nitric acid

2. Then add aqueous silver nitrate

Result: Yellow ppt

Nitrate, NO₃^- (In solution)

Test

1. Add aqueous sodium hydroxide

2. Then aluminium foil

3. Warm carefully 

Result: Ammonia produced

Sulphate, SO₄^2- (In solution)

Test

1. Acidify with dilute nitric acid

2. Then add aqueous barium nitrate

Result: White ppt

Sulfite, SO₃^2-

Test

1. Add small volume of acidified aqueous potassium manganate(VII)

Result:

The acidified aqueous potassium manganate(VII) changes colour from purple to colourless

Aluminium, Al³⁺ (Amphoteric)

Effect of Aqueous Sodium Hydroxide:

• Makes white ppt

• soluble in excess

• So when excess white ppt dissolves gives a colourless solution

Effect of aqueous ammonia:

• White ppt formed

• Insoluble in excess so no colour formed only ppt

Ammonium, NH₄⁺

Effect of Aqueous Sodium Hydroxide:

• Ammonia produced on warming

Effect of aqueous ammonia:

• Nothing

Calcium, Ca²⁺ 

Effect of Aqueous Sodium Hydroxide:

• White ppt

• Insoluble in excess so only ppt

Effect of aqueous ammonia:

• No ppt

• Or very slightly white ppt

Chromium(III), Cr³⁺ (Amphoteric)

Effect of Aqueous Sodium Hydroxide:

• Green ppt

• Soluble in excess

• Gives solution dark green colour if in excess

Effect of aqueous ammonia:

• Green ppt

• Insoluble in excess

Copper(II), Cu²⁺

Effect of Aqueous Sodium Hydroxide:

• Light blue ppt

• Insoluble in excess

Effect of aqueous ammonia:

• Light blue ppt

• Soluble in excess

• Giving dark blue solution when in excess

Iron(II), Fe²⁺

Effect of Aqueous Sodium Hydroxide:

• Green ppt

• Insoluble in excess

• ppt turns brown near surfaces on standing (means outer parts of ppt which are exposed to air, it is oxidising)

Effect of aqueous ammonia:

• Green ppt

• Insoluble in excess

• ppt turns brown near surfaces on standing

Iron(III), Fe³⁺

Effect of Aqueous Sodium Hydroxide:

• Red-brown ppt

• Insoluble in excess

Effect of aqueous ammonia:

• Red-brown ppt

• Insoluble in excess

Zinc, Zn²⁺ (Amphoteric)

Effect of Aqueous Sodium Hydroxide:

• White ppt

• Soluble in excess

• Giving colourless solution

Effect of aqueous ammonia:

• White ppt

• soluble in excess 

• Giving colourless solution