no detectable gain or loss of mass occurs in chemical reactions. Mass is conserved
law of definite proportions
in a given chemical compound, the elements are always combined in the same proportions by mass
law of multiple proportions
whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers
% mass of element
mass of elementmass of whole sample x 100%
emperical formula
simplest whole number ratio of atoms of each element in a compound