Ammonia vs Acids

Why it matters

Bring a bottle of ammonia near hydrochloric acid and watch white smoke appear out of thin air. This is not fog; it is a solid salt forming instantly from two gases.

The idea in plain words

Balance each pairing on the see-saw — set the coefficients until every atom tallies on both sides. Tip: sulphuric acid has two acidic protons, so it needs two ammonias.

Predict first

What is the nature of ammonia in this reaction?

Ammonia is a base because it accepts a hydrogen ion (proton) from the acid to form the ammonium ion.

• It acts as an acid, donating protons to HCl
• It acts as a base, accepting a proton from HCl — correct
• It is a neutral gas that physically mixes with HCl

What you do

Balance each pairing on the see-saw: NH₃ + HCl, 2NH₃ + H₂SO₄, NH₃ + HNO₃. Every time the base grabs a proton and a white ammonium salt is born.

Check yourself

Ammonia gas meets hydrogen chloride gas. What happens?

NH₃ + HCl → NH₄Cl. The base grabs the acid's proton and the salt appears as a white smoke or ring.

Ammonia is passed into sulphuric acid. What salt forms, and in what ratio?

Sulphuric acid has two acidic protons, so it needs two ammonias: 2NH₃ + H₂SO₄ → (NH₄)₂SO₄.

Ammonia reacts with nitric acid. What salt forms?

NH₃ + HNO₃ → NH₄NO₃ (ammonium nitrate, a widely used fertiliser).

Why do ammonia and acids react to form salts at all?

Ammonia is a base: it grabs a proton to become NH₄⁺, which pairs with the acid's anion to make an ammonium salt.

• They combine into a white solid, ammonium chloride (NH₄Cl) — seen as dense white fumes — correct
• A yellow precipitate forms
• No change — two gases cannot react
• A blue solution forms
• Ammonium sulphate, (NH₄)₂SO₄ — two NH₃ per H₂SO₄ — correct
• NH₄SO₄ — one NH₃ per H₂SO₄
• Ammonium hydrogensulphate, NH₄HSO₄ only
• Ammonium chloride, NH₄Cl
• Ammonium nitrate, NH₄NO₃ — correct
• Ammonium nitrite, NH₄NO₂
• (NH₄)₂NO₃
• Ammonium sulphate, (NH₄)₂SO₄
• Ammonia accepts a proton (H⁺) from the acid to form the ammonium ion, NH₄⁺ — correct
• Ammonia only donates an electron pair to make a covalent bond
• The two gases simply dissolve into each other