PERCENT PURITY!!

Sometimes, the reactant(s) we use is/are not pure.  So, before we can calculate much product will form, we need to use PERCENT PURITY to calculate how much reactant that actually is available to react.

% PURITY=Mass of Pure Substance/Mass of Impure Sample×100%

Below is a link of a video that demonstrates one example of the percent purity.
http://www.youtube.com/watch?v=15FOjmIUEy4&playnext=1&list=PL45C0C062682A839A