What mass (in grams) of potassium acetate, KC2H3O2, must be added to 140 mL of 0.010 M acetic acid to form a buffer solution with a pH of 4.5?

Question

What mass (in grams) of potassium acetate, KC2H3O2, must be added to 140 mL of 0.010 M acetic acid to form a buffer solution with a pH of 4.5?  
            (Ka (HC2H3O2)= 1.8 x 10-5)

DrBob222 · Answer

pH = pKa + log(b/a) 4.5 = 4.74 + log(base)/(acid) 4.5 = 4.74 + log(base)/0.01 Solve for (base) in moles/L. Convert to moles in 140 mL and convert that to grams KC2H2O2.