Question

2)_ To prepare a buffer solution with a pH of 3.45 What should be the mass of Sodium mandelate that should be added to 500ml of 1.00M mandelic acid solution?

Answer 1

Use the H-H equation. You will need to look pKa for mandelic aci

pH = pKa + log [(base)/(acid)] or pKa + log (b)/(a)
3.45 = pKa + log (b)/(1)
Solve for (b) in millimoles/mL = M. You've solved for M and you have mL (100 mL) so you solve for millimoles. Convert to mols and remember mol = grams/molar mass. You have molar mass and mols, calculate grams and you have it.