Tests for Ions

Question 1

Carbonate test

Answer 1

Add dilute nitric acid (HNO3)

CO3^2- (aq) + 2H⁺ (aq) ————> H2O (l) + CO₂ (aq)

effervescence observed

Question 2

Sulfate test

Answer 2

Add excess Ba ions (BaCl2 / BaNO3)

SO4^2- + Ba²⁺ ————> BaSO4

White ppt observed

(BaCO3 is also white ppt so carbonate test is carried out first)

Question 3

Halogen test

Answer 3

Add acidified silver nitrate (AgNO3)

X^- (aq) + Ag⁺ (aq) ————> AgX (s)

Cl^- = white ppt
Br^- = cream ppt
I^- = yellow ppt

Question 4

Ammonium test

Answer 4

Add dilute NaOH

NH₄⁺ + OH^- ————> NH₃ + H₂O

• ammonia can be smelled
• turns litmus/pH paper blue