Question

The largest change in pH for an effective buffer occurs when the base is how many times as concentrated as the acid?

(A) 25
(B) 10
(C) 5
(D) 40
(E) 8

Answer 1

(B) 10

Step-by-step explanation:

For the following reaction -

HA + H₂O ------> H₃O⁺ + A⁻

The pH equation for the above reaction is written as -

pH = pKa + log ( [base] / [acid] )

Hence , for a buffer to be effective , the value of pH should be equal to the value of pKa , i.e. ,

pH = pKa

Hence , the value of pH should be equal to the value of pKa , the log vale should be equal to 1 , which is done , when , the base is ten many times as that of the concentrated as the acid .

So , correct option is B .