Virtual CrezLab - Qualitative Analysis

The chemistry of a neutralisation reaction is essentially the chemistry of hydrogen and hydroxide ions in solution. The ionic equation for neutralisation:

H⁺ (aq) + OH^- (aq) -----> H₂O (l)

Le'ts look at the example of dilute hydrochloric acid added to sodium hydroxide solution.

Before mixing

After mixing

Hydrochloric acid dissociates completely in water to form a solution of hydrogen ions and chloride ions:

HCl (aq) ---> H⁺ (aq) + Cl^- (aq)

Sodium hydroxide also dissociates completely in water to form a solution of hydroxide and sodium ions.

NaOH (aq) ---> OH^- (aq) + Na⁺ (aq)

Hydrogen ions combine with hydroxide ions to form water molecules in the solution.

H⁺ (aq) + OH^- (aq) ---> H₂O (l)

This is the neutralisation reaction.
Sodium ions and chloride ions remain as free, mobile ions in the solution.

The sodium and chloride ions are called spectator ions because they do not take part in the neutralisation reaction.

Click on the animation to see this neutralisation process. You should see the spectator ions moving about randomly during the process.

The only chemical change which occurs is the attraction of the H⁺ and OH^- ions to form a water molecule.

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