Question

In a mixture of weak acid and its salt, the ratio of concentration of acid to salt is increased ten-fold. The pH of the solution
A. Decreases by one
B. Increases by one-tenth
C. Increases by one
D. Increases ten-fold

Answer 1

Correct Answer - A
It is buffer solution so,
`pH = pK_(a) + log.("Salt")/("Acid")`
`pH = pK_(a) - log.("Salt")/("Acid")` (Given `(["Acid"])/(["Salt"]) = 10 :1`)
`pH = pK_(a) - log 10`
`pH = pK_(a) = - 1`.