Back in chemistry class in high school I was working with a partner doing a chemical reaction. We measured the amounts of reagents well, but not perfect, and our yield suffered greatly. On the other hand my friend and his partner came up with quite a high yield. He told me it was because they measured each amount of reagent exactly.
So I wonder... Why are these reactions so dependent on perfect measuring of reagents? Why can't you just use more than enough of one reagent to completely react with the other and remove the excess reagent?
Also does this apply to all chemical reactions, or just a select few?