Molecular Formulas
1. A compound has the empirical formula C2H2 and a molecular weight of 78 grams/mole, what is the
molecular formula of this compound?
2. A sample of an unknown compound was analyzed and found to contain 42 grams of carbon and 14
grams of hydrogen. What is the molecular formula if the molar mass is 16 grams/mole?
3. A substance contains 22.5 percent by mass of phosphorus and 77.5% chlorine, what is the empirical
formula of this substance?
4. What is the empirical formula for a compound containing 5.75 g Na, 3.5 g N and 12.0 g Oxygen.
5. Hydrogen Peroxide has the empirical formula HO and a molar mass of 34 g/mole, what is its
molecular formula?
6. Octane, a compound of hydrogen and carbon has a molar mass of 114.0 g/mole and contains 18.0
g/mole of hydrogen, what is the molecular formula?
7. Vitamin C was analyzed and found to have a molar mass of 176 grams/mole and the following
percents by mass. Carbon 40.9%, Oxygen 54.5% and Hydrogen 4.6% what is the molecular formula
of vitamin C?
8. A compound with a molar mass of 92.0 g/mole, contains 30.4% nitrogen and 69.6% oxygen. Find the
molecular formula of the compound.
9. A pollutant from an automobile was found to consist of 50% sulfur and 50% by mass of oxygen.
What is the formula for this compound?
10. If gold is selling for $630 per troy ounce, how many atoms of gold can you buy for one penny? (1
troy ounce = 31.1 grams)