Final answer:
Upon combustion, 1 mol of CO2 is produced for each mole of carbon atoms in the original sample. The mass percents can be used to determine the amount of hydrogen and carbon present.
Step-by-step explanation:
Upon combustion, 1 mol of CO2 is produced for each mole of carbon atoms in the original sample. Similarly, 1 mol of H2O is produced for every 2 mol of hydrogen atoms present in the sample. The masses of carbon and hydrogen in the original sample can be calculated from these ratios, the masses of CO2 and H2O, and their molar masses. Because the units of molar mass are grams per mole, we must first convert the masses from milligrams to grams:
Thus for every 1g of the first compound there are 0.57g of oxygen and 0.429g of carbon. The mass of oxygen per gram carbon is:
Molar Masses of Compounds
The molecular formula of the compound carbon dioxide is CO2. One molecule of carbon dioxide consists of 1 atom of carbon and 2 atoms of oxygen. We can calculate the mass of one molecule of carbon dioxide by adding together the masses of 1 atom of carbon and 2 atoms of oxygen:
Similarly, for 1g of the second compound, there are 0.727g oxygen and 0.273g of carbon. The ration of mass of oxygen per gram of carbon is
The mass percents can be used to determine the amount of hydrogen and carbon are present.
3.00g * 0.112 = 0.336g of Hydrogen
7.33g * 0.273 = 2.001g of Carbon
Since one mole of H2O is made up of one mole of oxygen and two moles of hydrogen, if we have 0.017 moles of H2O, then we have 2*(0.017) = 0.034 moles of hydrogen. Since hydrogen is about 1 gram/mole, we must have 0.034 grams of hydrogen in our original sample.