A buffer solution is made by mixing weak acid HA `(K_(a)=10^(-6))` with its salt NaA in equal amount. What should be the amount of acid or salt that should be added to make 90 ml of buffer solution of buffer capacity 0.1 ?

Options

A. 10 mmoles
B. 22 mmoles
C. 9 mmoles
D. 11 mmoles

Answer

D

Explanation

For buffer capacity of 0.1 we should have `((c+0.1)/(c-0.1))=10`
where c is concentration of weak acid or salt in the buffer solution
So, `c+0.1=10 c-1` so `9c=1.1` or `c=1.1/9`
So, moles required for 90 ml solution =`1.1/9xx90xx10^(-3)` moles =11 m moles