Answer : The volume of sodium benzoate and benzoic acid solution mixed to prepare this buffer should be, 29.0 mL and 71 mL respectively.
Explanation :
Let the volume of sodium benzoate (salt) be, x
So, the volume of benzoic acid (acid) will be, (100 - x)
Using Henderson Hesselbach equation :
Now put all the given values in this expression, we get:
x = 29.0
The volume of sodium benzoate = x = 29.0 mL
The volume of benzoic acid (acid) = (100 - x) = (100 - 29.0) = 71 mL
Thus, the volume of sodium benzoate and benzoic acid solution mixed to prepare this buffer should be, 29.0 mL and 71 mL respectively.