Worksheet: % Composition and
Empirical Formulas
Name _________________
KEY
Part 1: % Composition
Calculate the percent composition of the following compounds. SHOW ALL WORK.
HCl
1.0 g + 35.5 g = 36.5 g
H
(1.0 g/36.5 g) x 100 % = 2.7 % H
Cl
(35.5 g/36.5 g) x 100 % = 97.3 % Cl
K2CO3
2 ( 39.1 g) + 12.0 g + 3 (16.0 g) = 138.2 g
K
(78.2 g/138.2 g) x 100% = 56.6 % K
C
(12.0 g/138.2 g) x 100 % = 8.68 % C
O
(48.0 g/138.2 g) x 100 % = 34.7 % O
Part 2: Empirical Formulas
Work each of the following problems. SHOW ALL WORK.
1. A compound is found to contain 63.52 % iron and 36.48 % sulfur. Find its
empirical formula.
? mol Fe = 63.52 g Fe !
? mol S = 36.48 g S
!
1 mol Fe
= 1.14 mol Fe
55.8 g Fe
1 mol S
= 1.14 mol S
32.1 g S
Fe1.14S1.14
FeS
2. In the laboratory, a sample is found to contain 1.05 grams of nickel and
0.29 grams oxygen. Determine the empirical formula.
? mol Ni = 1.05 g Ni !
? mol O = 0.29 g O !
1 mol Ni
= 0.0179 mol Ni
58.7 g Ni
1 mol O
= 0.018 mol O
16.0 g O
Ni0.0179O0.018
NiO
CHEMISTRY: A Study of Matter
© 2004, GPB
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