To find the percent composition of KCLO(2), calculate the total mass of the molecule: K has 39.0983 g/mol, Cl has 35.4532 g/mol, and O(2) is 31.99886 g/mol. This sums to 106.5501 g/mol. Next, find the percentages of each element: K would have (39.0983/106.5501) = 0.366948 or 36.6948%, Cl would have (35.4532/106.5501) = 0.332737 or 33.2737%, and O(2) would be (31.99886/106.5501) = 0.300318, or 30.0318%. Summing these three percentages gives 100.0003%, which is within the scope of a rounding error.
