Question

A weak acid `HA` has `K_(a) = 10^(-6)`. What would be the molar ratio of this acid and its salt with strong base so that `pH` of the buffer solution is `5`?
A. `1//10`
B. `10`
C. `1`
D. `2`

Answer 1

Correct Answer - B
`pH = pK_(a) + "log" ([A^(Theta)])/([HA])`
`5=6 + "log"([A^(Theta)])/([HA])`
`:. log.([HA])/([A^(Theta)]) = 1`
`:. ([HA])/([A^(Theta)]) = "Antilog" (1) = 10`.