Explain why all alkalis are bases, but not all bases are alkalis.
Alkalis are soluble bases, but only some bases are soluble in water. Bases that dissolve in water are alkalis.
A neutralisation reaction is a reaction between an acid and a base. Remember:
In acid-alkali neutralisation reactions, hydrogen ions from the acid react with hydroxide ions from the alkali. Here are the ions involved in the reaction of hydrochloric acid with sodium hydroxide solution:
H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) → Na+(aq) + Cl-(aq) + H2O(l)
Now remove the spectator ions, Cl-(aq) and Na+(aq). This leaves:
H+(aq) + OH-(aq) → H2O(l)
Pure water is neutral (its pH is 7). A neutral solution can be produced if the correct amounts of acid and alkali react together. The change in pH during a neutralisation reaction can be measured using a pH probe and meter, or estimated using universal indicator solution and a pH colour chart.