In: Chemistry
You have 525 mL of an 0.15 M acetic acid solution. What volume (V) of 2.00 M NaOH solution must you add in order to prepare an acetate buffer of pH = 5.32? (The pKa of acetic acid is 4.76.)
millimoles of acetic acid CH3COOH = 525 x 0.15 = 78.75
millimoles of base NaOH = V x 2.00 = 2V
CH3COOH + NaOH ----------------> CH3COONa + H2O
78.75 2V 0 0
78.75 - 2V 0 2V 2V
in the raction salt and acid remains so it forms acidic buffer.
pH = pKa + log [salt / acid]
5.32 = 4.76 + log (2V / 78.75 - 2V)
3.63 = (2V / 78.75 - 2V)
285.86 - 7.26 V = 2V
V = 30.87 ml
volume of NaOH = (V) = 30.87 mL