How To Calculate The Mass Percentage of Perchloric Acid Using Titration Method

June 20th, 2008

We can calculate the mass percentage of a substance using titration method. Titration formula is used to determine the mole-equivalent of the substance, if the mole equivalent of the substance is known we convert it into moles and then multiplying with molar mass to get the mass of the species. Dividing the actual mass of the substance with its original weight we have its mass percentage. Here the example

A 12.1 g sample of an aqueous solution of perchloric acid contains an unknown amount of the acid. If 20.4 mL of 0.450 M barium hydroxide is required to neutralize the perchloric acid, what is the percent by weight of perchloric acid in the mixture?

First we calculate the mole of the perchloric acid (HClO4) using titration formula. Remember V x N (volume multiply with normality produce mole-equivalent or meq), and we convert molarity of Ba(OH)2 solution into normality because Ba(OH)2 has two hydroxide ions thus 0.450 M of barium hydroxide is equal to 0.9 N.

V x N acid = V x N base
meqacid = V x N base
meq acid = 20.4 mL x 0.9 N
meq scid = 18.36 milli-equivalent

because HClO4 has one ion hydrogen thus one equivlent of HClO4 is equal to one mole of HClO4, then 18.36 milli-equivalents of HClO4 = 18.36 millimoles of HClO4. The mass of HClO4 can be calculate as

mass of acid (HClO4)
= moles x molar mass
= 18.36 mmol x 100.458
= 1844.409 mgr
= 1.844409

then the mass percentage of HClO4 are
= mass of HClO4 / mass of sampel x 100%
= 1.844409/12.1x 100%
= 15.243 %

from these calculation we get that the mass percentage of perchloric acid in the sample using titration calculation are 15.243%

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