Empirical & Molecular Formulas – show all of your work!
1. What is the empirical formula of a compound that contains 62.1% C, 5.21%H, 12.1% N and the remaining
percentage is Oxygen.
2. What is the molecular formula of a compound where the empirical formula is C2H4O and the molar mass
of the molecular formula is 88 g mol-1?
3. Caffeine, a stimulant found in coffee, contains 49.5% C, 5.15% H, 28.9% N and 16.5% O by mass. The
molecular formula has a molar mass of 194.22 g mol-1. Determine the empirical and molecular formulas
for caffeine.
4. Nicotine, a component of tobacco, is composed of C, H, and N. A 5.2500mg sample of nicotine was
combusted, producing 14.242 mg of CO2 and 4.083 mg of H2O. What is the empirical formula of nicotine?
If the substance has a molar mass of 160 +/- 5 g mol-1, what is the molecular formula?
5. Epsom salts, a strong laxative used in veterinary medicine, is a hydrate. The formula for the hydrate is
MgSO4
.
X H2O, where X indicates the number of moles of H2O per mole of MgSO4. When 5.061 g of this
hydrate is heated to 250oC, all of the water is lost, leaving 2.472 g of MgSO4. What is the value of X?