Nitrides Meet Water
Generate ammonia from magnesium nitride and water
What this lesson covers
Why it matters
A greenish-yellow powder of magnesium nitride meets warm water, releasing a gas with a sharp, choking smell. The solution turns cloudy as a white precipitate forms.
The idea in plain words
Balance the equation: Mg₃N₂ + H₂O → Mg(OH)₂ + NH₃. Note the 1:6:3:2 ratio.
Predict first
What gas is released when magnesium nitride reacts with water?
Metal nitrides hydrolyse to form ammonia gas and the corresponding metal hydroxide.
- Nitrogen gas (N₂)
- Ammonia gas (NH₃) — correct
- Hydrogen gas (H₂)
What you do
Add warm water to the magnesium nitride. Observe the white precipitate and test the gas evolved.
Check yourself
How do you confirm the gas produced is ammonia?
Ammonia is alkaline; it turns moist red litmus blue.
What is the white precipitate formed in the reaction?
The reaction produces Mg(OH)₂, which is sparingly soluble and appears as a white precipitate.
Why is this reaction classified as double decomposition?
Mg₃N₂ and H₂O exchange partners: Mg pairs with OH, and N pairs with H.
- It relights a glowing splint
- It turns moist red litmus paper blue — correct
- It turns lime water milky
- Magnesium oxide (MgO)
- Magnesium hydroxide (Mg(OH)₂) — correct
- Magnesium carbonate (MgCO₃)
- Because two compounds exchange ions to form two new compounds — correct
- Because a single compound breaks down into elements
- Because a metal displaces hydrogen from water