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

(B) 10

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 .