Calculate the change in pH to three decimal places that occurs when 0.50 mmol of a strong acid is added to 100 mL of
(a) 0.0200 M lactic acid + 0.0800 M sodium lactate.
(b) 0.0800 M lactic acid + 0.0200 M sodium lactate.
(c) 0.0500 M lactic acid + 0.0500 M sodium lactate.