Question

The dissociation constants of a weak acid HA and weak base BOH are $2\times {10}^{-5}$ and $5\times {10}^{-6}$ respectively. The equilibrium constant for the neutralisation reaction of the two is :

• A. $1.0\times {10}^4$
• B. $1.0\times {10}^{-4}$
• C. $1.0\times {10}^{-10}$
• D. $2.5\times {10}^{-1}$

Answer 1

The correct option is A $1.0\times {10}^4$

For the neutralization reaction of a weak acid and weak base, the expression for the equilibrium constant K is as given below.

$K=\frac{K_a\times K_b}{K_w}$

By substituting values in the above expression, we get

$K=\frac{2\times {10}^{-5}\times 5\times {10}^{-6}}{1\times {10}^{-14}}=1.0\times {10}^4$.