Download Empirical/Molecular Formula Practice

Chemistry 1211 Empirical/Molecular Formula Practice
1. A compound is analyzed and found to be 12.5% hydrogen and
87.5% nitrogen. Find the empirical formula. Ans: NH
2
2. Methyl salicylate is a common “active ingredient” in liniments
such as Ben-Gay. It is also known as oil of wintergreen. It is
made up of carbon, hydrogen, and oxygen atoms. When a sample
of methyl salicylate weighing 5.287 g is burned in excess oxygen,
12.24 g of carbon dioxide and 2.505 g of water are formed. What
is the empirical formula for oil of wintergreen? Ans: C H O
8
8
3
3. A compound is 69.6% Fe and the rest is O. Find the empirical
formula. Ans: Fe O
2
3
4. If 2.643 g of antimony reacts with 0.521 g oxygen. What is the
simplest formula? Ans: Sb O
2
3
5. A compound is 55.3% potassium, 14.6% phosphorous and the
rest is oxygen. What is the empirical formula? Ans: K PO
3
4
6. Caffeine is 49.5% carbon, 5.15% hydrogen, 28.9% nitrogen and
16.5% oxygen. The molecular weight is about 195g/mole. What
is the molecular formula? Ans: C H N O
8
10
4
2
7. Combustion (burning with oxygen) of toluene, a common
organic solvent, gives 5.86 mg of CO2 and 1.37 mg of H2O. If the
compound contains only carbon and hydrogen, what is its
empirical fomula? Ans: C H
7
8
8. Cadaverine, produced by the action of bacteria on meat, is
58.55% C, 13.81% H, 27.40% N. MW = 102.2 g/mole. What is
its molecular formula? Ans: C H N
5
14
2