Question

10 ml of 0.2 M acid is added to 250 ml of a buffer solution with pH = 6.34. The pH of the solution
becomes 6.32. The buffer capacity of the solution is
(B) 0.2
(C) 0.3
(D) 0.4
(A) 0.1​

Answer 1

The buffer capacity of the solution is 0.4

Given -

• Volume of an acid = 10 mL
• Concentration of an acid = 0.2 M
• Volume of buffer solution = 250 mL
• pH of buffer solution = 6.34
• pH of solution = 6.32

We know that buffer capacity is the ratio of number of moles of acid or base added per liter to the change in pH.

Buffer capacity is denoted by β. So,

Number of moles of acid or base added per liter is = 0.2 × 10 × 1000 /1000 × 250 = 0.008

Change in pH = 6.34 - 6.32 = 0.02

β = 0.008/0.02 = 0.4