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Percent Composition and Molecular Formula Worksheet
1. Calculate the percent of nitrogen in urea, NH
2
CONH
2
.
2. Calculate the percentage of water in zinc sulfate heptahydrate.
3. Calculate the percentage of oxygen in potassium chlorate.
4. Calculate the percentage of tin in potassium stannate trihydrate, K
2
SnO
3
•2H
2
O
Write the molecular formulas of the following compounds:
5. A compound with an empirical formula of C
2
OH
4
and a molar mass of 88 grams per mole.
6. A compound with an empirical formula of C
4
H
4
O and a molar mass of 136 grams per mole.
7. A compound with an empirical formula of CFBrO and a molar mass of 254.7 grams per mole.
8. A compound with an empirical formula of C
2
H
8
N and a molar mass of 46 grams per mole.
Answer the following questions:
9. The percentage composition of acetic acid is found to be 39.9% C, 6.7% H, and 53.4% O. Determine the
empirical formula of acetic acid.
10. The molar mass for question #9 was determined by experiment to be 60.0 g/mol. What is the molecular
formula?
11. What’s the empirical formula of a molecule containing 18.7% lithium, 16.3% carbon, and 65.0% oxygen?
12. A 50.51 g sample of a compound made from phosphorus and chlorine is decomposed. Analysis of the
products showed that 11.39 g of phosphorus atoms were produced. What is the empirical formula of the
compound?
13. When 2.5000 g of an oxide of mercury, (Hg
x
O
y
) is decomposed into the elements by heating, 2.405 g of
mercury are produced. Calculate the empirical formula.
14. The compound benzamide has the following percent composition. What is the empirical formula?
C = 69.40 % H= 5.825 % O = 13.21 % N= 11.57 %
15. A component of protein called serine has an approximate molar mass of 100 g/mole. If the percent
composition is as follows, what is the empirical and molecular formula of serine?
C = 34.95 % H= 6.844 % O = 46.56 % N= 13.59 %
16. Aniline, a starting material for urethane plastic foams, consists of C, H, and N. Combustion of such
compounds yields CO
2
, H
2
O, and N
2
as products. If the combustion of 9.71 g of aniline yields 6.63 g H
2
O and
1.46 g N
2
, what is its empirical formula?
17. The molar mass of aniline is 93 g/mol. What is its molecular formula?
Name _______________________________
Date ____________________ Block _______
