Characteristics of Ammonia
- Ammonia gas can turn a moist red litmus paper to blue.
- As an alkali, ammonia can react with acid to form salt and water.
H2SO4(aq) + 2NH3(aq) → (NH4)2SO4(aq)
HNO3(aq) + NH3(aq) → NH4NO3(aq)
H3PO4(aq) + 3NH3(aq) → (NH4)3PO4(aq)
- Ammonia dissolve into water to form ammonium and hydroxide ion.
NH3 + H2O→ NH4+ + OH–
- The hydroxide ion can react with many kinds of positive ion to form precipitate.
Mg2+ + 2OH– → Mg(OH)2
Fe2+ + 2OH– → Fe(OH)2
Al3+ + 3OH– → Al(OH)2
Testing for Ammonia
- Ammonia is the only common alkaline gas so it can be identified with moist red litmus paper turning blue.
- Concentrated ammonia when reacts with concentrated hydrochloric acid produces white fume.
Ammonia gas + Hydrogen chloride gas → ammonium chloride
NH3 (g) + HC1 (g) → NH4C1