Acidity constants Weak acids in equilibrium. |
Acid/base reactions in water are also examples of equilibrium reactions. Consider the ionisation of the weak acid ethanoic acid. The equilibrium expression for this above reaction is
The acidity
constants are an indication of the strength of the acid, the higher the
acidity constant the greater the strength of the acid. |
Lets try some
examples involving the Ka. Step 1 Notice
that the Ka is very low indicating a weak acid. When an acid is weak
we assume negligible ionisation. We assume that the concentration of
acid present at equilibrium is 0.4M.
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