Posted by San on .
A 0.100g sample of a compound containing C, H, and O is burned oxygen producing 0.1783 g of CO2 and 0.0734 g of H2O. Determine the empirical formula of the compound.
First you must determine how much oxygen is there and you do that by converting H2O to H, CO2 to C, adding C and H and subtracting from 0.1 to find O.
0.1783 CO2 (molar mass C/molar mass CO2) = ?? (Approximately 0.049 but you need to do it more accurately than I've estimated.)
0.0734 g H2O x (2*molar mass H/molar mass H2O) = ??(approximately 0.0083
Then 0.1 - C - H = g O.
Now convert grams of each to moles.
moles = grams/molar mass
moles C = ?
moles H = ?
moles O = ?
To find the empirical formula, determine the mole ratio of the elements to each other with the smallest being 1.00. The easy way to do that is to divide the smallest number by itself, then divide the other two numbers by the same small number. Round to whole number UNLESS the fraction is between 0.2 and 0.8. If that is the case, multiply by 1, 2, 3, 4, etc until all of the numbers come out to whole numbers (or close enough to round to whole numbers). That will be the empirical formula.
Post your work if you get stuck.