1. Molecular Formula
Percent Composition

2. What is the % composition of H2SO4 to 3 sig figs?
H x = 2.02 g
S x = 32.1 g
O x = 64.0 g
H2SO4 = g
% H = 2.02 g x 100 % = %
98.12 g
% S = 32.1 g x 100 % = %
% O = 64.0 g x 100 % = %
99.9 %

3. Calculate the percentage composition for Ca3(PO4)2.5H2O to 3 sig figs.
3 Ca 3 x = g
2 P 2 x = g
13 O 13 x = g
10 H 10 x = g
Ca3(PO4)2.5H g
% Ca = x 100 % = 30.0 %
400.4
% P = x 100 % = 15.5 %
% O = x 100 % = 51.9 %
% H = x 100 % = 2.52 %
99.9 %

4. Empirical Formula
Molar Mass
Molecular Formula
Molecular Mass
C4H8NO
86.08 g/mol
C12H24N3O3
g/mol
C7H12
96.12 g/mol
C14H24
g/mol
360.4 g/mol
C4H8O
72.08 g/mol
C20H40O5
78.06 g/mol CH
13.01 g/mol
C6H6
78.06
192.24
360.4
= 6
= 2
= 5
13.01
96.12
72.08

5. A compound is found to contain 30. 8 % C, 4. 27 % H, 23. 9 % N, and 41
A compound is found to contain 30.8 % C, 4.27 % H, 23.9 % N, and 41.0 % O. The molecular mass is g/mole. Determine the empirical and molecular formulas.
30.8 g C x 1 mol = mol
12.0 g =
= 3
1.707 mol
4.27 g H x 1 mol = mol g
= 5 =
1.707 mol
x 2 =
23.9 g N x 1 mol = mol g
= 2
= 1
1.707 mol
41.0 g O x 1 mol = mol g
= 3 =
1.707 mol
C3H5N2O3
117.0 g/mole
x 4 =
468.0 g/mole
C12H20N8O12

6. A compound is found to contain 66. 35 g C, 17. 54 g H, 33
A compound is found to contain g C, g H, g N, and g O. The molecular mass is g/mole. Determine the empirical and molecular formulas.
66.35 g C x 1 mol = mol
12.0 g =
= 7
2.369 mol
17.54 g H x 1 mol = mol g
= 22 =
2.369 mol
x 3 =
33.17 g N x 1 mol = mol g
= 3
= 1
2.369 mol
66.22 g O x 1 mol = mol g
= 5 =
2.369 mol
C7H22N3O5
g/mole
x 2 =
g/mole
C14H44N6O10
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