Acid-base equilibria

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I have an equation which involves mixing sodium hyroxide and hydrochloric acid and I need to write an ionic equation. But sodium chloride is soluble and water isn't a precipitate? Does there have to be a precipitate?

No, there doesn’t have to be a precipitate – there is nothing here which is insoluble in water. This is a neutralisation reaction.
 
The full equation is:
 
HCl (aq) + NaOH (aq) --> NaCl (aq) + H₂O (l)
 
To get the ionic equation, write it out again showing the ions in the ionic substances but leaving the water unchanged because it isn’t ionic.
 
H⁺(aq) + Cl^- (aq) + Na⁺ (aq) + OH^- (aq) -> Na⁺ (aq) + Cl^- (aq) + H₂O (l)
 
Now eliminate all those ions which haven’t really done anything – ie they are there on both sides of the equation. These are sometimes called ‘spectator ions’. In this case they are the sodium ions and the chloride ions.
 
What we are left with is:
 
H⁺ (aq) + OH^- (aq) --> H₂O (l)
 
This is the ionic equation for any reaction between an acid and an alkali.

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updated: 01 December 2006