Empirical Formula Problems
Regents Chemistry
Name ___________________________________
For the following problems, show ALL work.
1. A substance was analyzed and it was determined that it was composed of 13% Lithium, 26.4%
nitrogen and 60.6% oxygen. What is the empirical formula of the substance?
2. What is the empirical formula of a compound that contains 46.7% silicon, and 53.3% oxygen?
3. Our 10.0 g sample of a pure substance is found to contain 2.25 g of magnesium, 3.24 g of
chlorine and 4.46 g of oxygen. What is the empirical formula of the substance?
(HINT – Think about the first step in a %  formula problem, and this problem gets very easy!)
4. If the empirical formula of a substance is CH3 and the molecular mass of the substance is 45.0
g/mole, what is the molecular formula of the substance?
5. What is the molecular formula of a substance that has an empirical formula of CH4N, and a
molecular mass of 60.4 g/mole?
6. If the empirical formula is CH and the gram molecular mass of a substance is 52.0 g/mole,
what is the empirical formula?
Percent composition formula
7. What is the percent by mass of lithium in lithium nitrite?
8. Determine the percent by mass of oxygen in gold (III) nitrate.
Grams and Moles
9. What is the mass of 2.50 moles of lithium nitrite?
10. How many moles are in a 156.0 g sample of gold (III) nitrate?