Equilibrium Question 853
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
Options:
A) $ 1.0\times 10^{4} $
B) $ 1.0\times {10^{-4}} $
C) $ 1.0\times {10^{-10}} $
D) $ 2.5\times {10^{-1}} $
Show Answer
Answer:
Correct Answer: A
Solution:
$ HA+BOH\rightarrow BA+H_2O $
$ \therefore K_{H}=\frac{K_{w}}{K_{a}\times K_{b}}. $ The inverse of $ K_{H} $ is $ K_{c}=\frac{K_{a}\times K_{b}}{K_{w}}. $
$ =\frac{2\times {10^{-5}}\times 5\times {10^{-6}}}{1\times {10^{-14}}}=1.0\times 10^{4} $
