Question

Why is acetic acid called weak acid?

Answer 1

Because at equilibrium the parent acid remains largely as the parent acid........

Explanation:

The strength of an acid, `HX`, is assessed on the basis of the completion of the equilibrium reaction.........

`HX+H_2O rightleftharpoons H_3O^(+) + X^-`

For stronger acids, the equilibrium lies to the RIGHT as written.

For acetic acid, we write the equilibrium as..........

`H_3C-CO_2H(aq) +H_2O(l) rightleftharpoons H_3O^(+) + H_3C-CO_2^-`

And for acetic acid, `K_a=([H_3O^+][AcO^-])/([HOAc])=10^(-4.76)`....

Given the equilibrium constant, most of the acetic acid is present as `HOAc`. This specifies a weak acid as per the given definition.....