Use the Henderson-Hasselbalch equation for a.
pH = pKa + log(base)/(acid)
b.
millimols acid = 200 x 0.1 = 20
millimols base = 300 x 0.075 = 22.5
millimols HCl added = 20 x 0.4 = 8
Set up an ICE chart.
.........lactate + H^+ ==> lactic acid
I..........22.5....0........20
added..............8...........
C..........-8.....-8........+8.....
E..........14.5....0........28
Plug the E line into another HH equation and solve for pH. Adding acid should decrease the pH.
(a)What is the pH of a solution made by combining 200 mL of 0.1 M Lactic Acid with 300 mL of 0.075 M sodium lactate? (b) If 20 mL of 0.4 M HCl is added to the solution from (a) what is the resulting pH?
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