chemistry
posted by Audrey .
How many grams of potassium formate, KHCOO, must be added to 500 mL of a .07 M solution of HCOOH to produce a buffer solution with a pH of 3.50?
given: Ka of HCOOH=1.8 x 10^4

Use the HendersonHasselbalch equation and solve for (base)/(acid) concns. Calculate moles acid in the problem, substitute into the B/A ratio and solve for base concn. Then g = moles x molar mass for HCOOK grams.