1.

Explain about the strength of acid on the basis of K_a value.

Answer»

Solution :(i) `K_a` is called the ionisation CONSTANT or dissociation constant of the acid. It measures the strength of an acid.
(ii) Acids such as `HCl,HNO_3` are almost COMPLETELY ionised and hence they have high `K_a` value i.e, `K_a` for HCl at `25^@C` is `2 times 10^6`
(iii) Acids such formic acid and acetic acid are partially ionised in solution and have LOW `K_a` value i.e., `K_a` for acetic acid `1.8 times 10^-5` at`25^@C`
(iv) Acids with `K_a` value greater than ten are considered as strong acids and LESS than one considered as weak acids.


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