Acetic acid is a weak acid with a pka of 4.76. what is the concentration of acetic acid in a buffer solution of 0.2m at ph 4.9. give your answer in m but as a numeral only to 3 decimal places.

0.084 M

Explanation:

Using the Henderson-Hasselbalch equation for a buffer ( a buffer is solution contain a weak acid and it conjugate base; the solution resist change in pH)

pH = pKa + log ( base/acid)

4.9 - 4.76 =log ( base / acid)

10^0.14 =  ( base / acid)

1.38 = (base / acid)

since there is 0.2 M in the buffer solution

the concentration of acid =   × 0.2 = 0.084 M