Posted by Mike on Monday, October 15, 2007 at 10:33pm.
A 0.01205 mg sample of an unknown compound was found to contain 0.0001 mg of H, 0.0043 mg of Cl, and 0.0077 mg of O. It was also determined that the unknown compound had a molecular weight of 100.46 g/mol. What is the molecular formula for this compound?

chem  DrBob222, Monday, October 15, 2007 at 10:39pm
Convert grams of each element into mols. mols = grams/atomic mass.
Then take the ratio of the elements. The easiest way to do this is to divide the smallest # mols by itself (thus making it 1.00), then divide the other mol values by the same smallest number. That will get you the mole ratios and the empirical (simplest) formula. To find the molecular formula, divide the molecular weight of 100.46 by the formula weight of the empirical formula, round to the nearest whole number, then multiply the empirical formula by this whole number. Post your work if you get stuck and I can help you through it. 
chem  Mike, Monday, October 15, 2007 at 10:48pm
thanks a million for the help.