CHEM 1021 Lecture Notes - Lecture 4: Aluminium Sulfate, Unified Atomic Mass Unit, Chalcopyrite
Document Summary
Compounds as 2 or more different elements chemically combined through the use of bonds. Law of definite proportions - the elements in a compound are always present in the same proportion of whole number units. Fractional composition - the expression of a ratio as a fraction (think the 2 oranges out of the 5 fruits in the painting; fruits are oranges) The comparison of one part to a whole (ie. mass, percentage) Percent composition is a ratio out of 100 (think of 100 as a clear basis of reference for further calculations and analysis) Mathematically, % of a in a compound = (amount of a / total amount of substance) x 100. For example, chalcopyrite (fool"s gold) is a compound made up of 34. 6% copper, 30. 5% iron, and 34. 9% sulfur (totals 100% for total composition) Percent by mass h in h2o = ( 2(1. 008 amu h) / 18. 016 amu (h20)) x 100 = 11. 22 %
