Acid

1
Acid Base Titrations
A titration is a quantitative study of a
neutralization reaction. The parameters involved
are 1.moles of the acid (from M x V, or
mass/molar mass if its a solid) 2.moles of the
base (also from M x V) 3.the reaction mole ratio
(from the balanced equation) Example 1 In the
reaction Ca(OH)2 2 HCl ? 2 H2O CaCl2, an
equivalence point is reached after 29.23 mL of
0.0725 M HCl is added to 25.00 mL of Ca(OH)2.
Find the Ca(OH)2. moles of HCl M x V
0.0725 mol x 0.02923 L L
2.12 x 10-3 mol
2
moles of Ca(OH)2 moles of HCl x mole ratio
2.12 x 10-3 mol HCl x 1 mol Ca(OH)2 2
mol HCl 1.06 x 10-3 mol Ca(OH)2
moles volume 1.06 x 10-3 mol
0.02500 L 4.24 x 10-2 M Titrations can be
used to determine the amount of pure acid (or
base) in a mixture, since only the acid (or base)
is neutralized.
3
Example The ASA (a monoprotic acid with a molar
mass of 180.2 g/mol) in a 325 mg Aspirin tablet
is neutralized by the addition of 22.25 mL of
0.0711 M NaOH. Find the percentage purity of the
tablet. moles of NaOH M x V 0.0711
mol x 0.02225 L L 1.58 x 10-3
mol moles of ASA moles of NaOH (since acid is
monoprotic, mole ratio will be 11) 1.58 x
10-3 mol mass of ASA 1.58 x 10-3 mol x 180.2
g mol
2.85 x 10-1 g
4
2.85 x 10-1 g x 1000 mg 1 g 285 mg ASA
in tablet pure mass x 100 total
mass 285 mg x 100 325 mg Read other
examples, p.155-157 (including Experimental
Note) Exercises 94 96, 98, 100, 101, 103, 105,
106
87.7