Question

Hydrochloric acid is neutralised by both sodium hydroxide solution and ammonia solution. In both cases, you get a colourless solution which you can crystallise to get a white salt - either sodium chloride or ammonium chloride.

Answer 1

Your description is correct. Brief summary, chemical equations and key differences:

Reactions
- With sodium hydroxide (strong base):
HCl + NaOH → NaCl + H2O
Ionic view: H+ + OH− → H2O (Na+ and Cl− remain as spectator ions)

- With ammonia (weak base):
HCl + NH3 → NH4Cl
Ionic view: H+ + NH3 → NH4+

Observations
- Both give colourless solutions that can be evaporated/crystallised to give white crystalline salts (NaCl or NH4Cl).
- In solution both contain Cl−, so tests for chloride (e.g., AgNO3 → white AgCl precipitate) behave the same.

Important differences
- Base type: NaOH is a strong base (provides OH−), NH3 is a weak base (is protonated to NH4+).
- Product composition: neutralisation with NaOH produces water as well as NaCl; with NH3 you form the ammonium ion (NH4+) — no net water formation in the simple equation.
- Thermal behaviour: NaCl is thermally stable; NH4Cl decomposes/sublimes on strong heating (NH4Cl ⇌ NH3 + HCl), so crystallisation/evaporation of ammonium chloride needs gentler conditions.
- Tests to distinguish salts:
- Flame test: Na+ gives a strong yellow flame (NaCl). NH4+ gives no characteristic flame colour.
- Detection of NH4+: add a strong base (e.g., NaOH) to the solid or solution and gently heat — if NH4+ is present, NH3 gas is evolved and will turn damp red litmus blue (or give the characteristic smell; use care).
- Both give AgCl with AgNO3 because both contain Cl−.

Safety notes
- HCl and NaOH are corrosive; NH3 solution is irritating and pungent. Work in a fume hood or well-ventilated area, use gloves and eye protection.