Question

Determine a pH range for which a buffer system containing benzoic acid would be appropriate. Devise a recipe for preparing 1.0 L of buffer solution that contains a total of 0.150 mol of buffer components (acid plus conjugate base) and has a pH of 4.48. The conjugate base will be added in the form of sodium benzoate.


i dont really know what this problem is asking me to do or how to approach it?

Answer 1

The pH range is pKa for benzoic acid +/- 1 and you will need to look up the pKa for benzoic acid.

Where are you having trouble with the problem. You have two ways to go.
1. Start with benzoic acid and add enough NaOH to get the pH you want, or
2. Start with benzoic acid and add sodium benzoate.

Which is the way you've been doing it.

Answer 2

so i found pH and pKa then set up molbase+molacid=.150
then solved what melbase/molacid is and did simple algebra

i got .099?

Answer 3

OK I don't know what pKa you are using but I obtained 0.0984 for mols base using pKa of 4.20.
mol = grams/molar mass.
You know mols and you know molar mass, solve for grams.
grams = 0.099 x 122 = ?