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Title: Percent composition of compounds
Description: This material deals with learning how to determine the percent composition of compounds. It outlines in detail the procedures for arriving at the correct percent composition.

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Study Guide

Percent Composition

Percent Composition
Percent composition is the ratio of the mass of an element in a compound
...

Example 1
...

Step 1
...
In this case, it is NH 3
Step 2
...
The molar mass of a compound is simply the
sum of the masses of the contributing elements
...

(1mol H) (

1
...
00g/mol (we multiply the molar mass of hydrogen by 3 because there are
three hydrogen atoms in the formula)

(1mol N) (

14
...
00g/mol

Molar mass of NH3 = total mass contributed by hydrogen + total mass contributed by Nitrogen
Molar mass of NH3 = 3
...
00g =17
...

Element in the
compound

Molar mass of the
element

Hydrogen
Nitrogen

1
...
00g/mol
Molar mass of NH3

Subscript

3
1

Total mass
contributed by the
element
3
...
00g/mol
17
...
Apply the formula for percent composition for each element in the compound
...
00𝑔/π‘šπ‘œπ‘™)

Percent Hydrogen = 17
...
00𝑔/π‘šπ‘œπ‘™

Percent Hydrogen = 17
...
176) x100
Percent Hydrogen = 17
...
Dela Cruz

Study Guide

Percent Composition

Percent Nitrogen
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π‘π‘–π‘‘π‘Ÿπ‘œπ‘”π‘’π‘›)

Percent Nitrogen = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π΄π‘šπ‘šπ‘œπ‘›π‘–π‘Ž x 100
1(14
...
00𝑔/π‘šπ‘œπ‘™ x100
14
...
00𝑔/π‘šπ‘œπ‘™ x100
Percent Nitrogen = (
...
4%
The results of the calculations mean that Ammonia is 82
...
6% Hydrogen
by mass
...
Determine the percent composition of H2SO4
...
Calculate the molar mass of H2SO4
...
00g/mol
32
...
00g/mol
Molar mass of H2SO4

2
1
4

Total mass
contributed by the
element
2
...
06g/mol
64
...
06g/mol

Step 2
...

Percent Hydrogen
Percent Hydrogen =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π»π‘¦π‘‘π‘Ÿπ‘œπ‘”π‘’π‘›)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝐻2 𝑆𝑂4
2(1
...
06𝑔/π‘šπ‘œπ‘™ x100
2
...
06𝑔/π‘šπ‘œπ‘™ x100
Percent Hydrogen = (
...
0%
Percent Sulfur
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π‘†π‘’π‘™π‘“π‘’π‘Ÿ)

Percent Sulfur = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝐻 𝑆𝑂 x 100
2 4
1(32
...
06𝑔/π‘šπ‘œπ‘™ x100
32
...
06𝑔/π‘šπ‘œπ‘™ x100
Percent Sulfur = (
...
7%
2

Reymon T
...
06𝑔/π‘šπ‘œπ‘™
64𝑔/π‘šπ‘œπ‘™

Percent Oxygen = 98
...
653) x100
Percent Oxygen = 65
...
3% Oxygen, 32
...
0% Hydrogen
...
Determine the percent composition of Ammonium Sulfite- (NH4)2SO3
...
In the case of Ammonium
sulfite, we see that the entire polyatomic cation is multiplied by 2 as shown by the subscript after
the closing parenthesis highlighted in red
...

(NH4)2SO3
Step 1
...
00 g/mol

1 x 2 (subscript outside

Hydrogen

1
...
00 g/mol

the parenthesis)

8 g/mol

the parenthesis)

Sulfur
Oxygen

32
...
00 g/mol
Molar mass of (NH4)2SO3

1
3

32
...
00 g/mol
116
...
Apply the percent composition formula to each of the elements in the compound
...
00𝑔/π‘šπ‘œπ‘™)

Percent Nitrogen = 116
...
00𝑔/π‘šπ‘œπ‘™

Percent Nitrogen = 116
...
241) x100
Percent Nitrogen = 24
...
Dela Cruz

Study Guide

Percent Composition

Percent Hydrogen
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π»π‘¦π‘‘π‘Ÿπ‘œπ‘”π‘’π‘›)

Percent Hydrogen = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ (𝑁𝐻 ) 𝑆𝑂 x 100
4 2 3
8(1
...
06𝑔/π‘šπ‘œπ‘™ x100
8
...
06𝑔/π‘šπ‘œπ‘™ x100
Percent Hydrogen = (
...
9%
Percent Sulfur
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π‘†π‘’π‘™π‘“π‘’π‘Ÿ)

Percent Sulfur = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ (𝑁𝐻 ) 𝑆𝑂 x 100
4 2 3
1(32
...
06𝑔/π‘šπ‘œπ‘™ x100
32
...
06𝑔/π‘šπ‘œπ‘™ x100
Percent Sulfur = (
...
6%
Percent Oxygen
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝑂π‘₯𝑦𝑔𝑒𝑛)

Percent Oxygen = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ (𝑁𝐻 ) 𝑆𝑂 x 100
4 2 3
3(16
...
06𝑔/π‘šπ‘œπ‘™ x100
48
...
06𝑔/π‘šπ‘œπ‘™ x100
Percent Oxygen = (
...
4%
Ammonium sulfite is composed of 41
...
6% Sulfur, 6
...
1%
Nitrogen by mass
...
Dela Cruz

Study Guide

Percent Composition

Practice Exercises
Directions: Determine the percent composition of the following compounds
...
Ba(OH)2
2
...
CaCO3
4
...
KMnO4

Solution
1
...
33 g/mol
16
...
00 g/mol
Molar mass of Ba(OH)2

1
2
2

Percent Barium
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π΅π‘Žπ‘Ÿπ‘–π‘’π‘š)

Percent Barium = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π΅π‘Ž(𝑂𝐻) x 100
2
1(137
...
33𝑔/π‘šπ‘œπ‘™ x100
Percent Barium =

137
...
33𝑔/π‘šπ‘œπ‘™

Percent Barium = (
...
2%
Percent Oxygen
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝑂π‘₯𝑦𝑔𝑒𝑛)

Percent Oxygen = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π΅π‘Ž(𝑂𝐻) x 100
2
2(16
...
33𝑔/π‘šπ‘œπ‘™ x100
32
...
33𝑔/π‘šπ‘œπ‘™ x100
Percent Oxygen = (
...
7%
Percent Hydrogen
Percent Hydrogen =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π»π‘¦π‘‘π‘Ÿπ‘œπ‘”π‘’π‘›)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π΅π‘Ž(𝑂𝐻)2
2(1
...
33𝑔/π‘šπ‘œπ‘™ x100
2
...
33𝑔/π‘šπ‘œπ‘™ x100
Percent Hydrogen = (
...
2%
5

Reymon T
...
33 g/mol
32
...
00 g/mol
171
...
2% Hydrogen, 18
...
2%
Barium
2
...
31 g/mol
32
...
00 g/mol
Molar mass of MgSO4

1
1
4

Total mass
contributed by the
element
24
...
06 g/mol
64
...
37 g/mol

Percent Magnesium
Percent Magnesium =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π‘€π‘Žπ‘”π‘›π‘’π‘ π‘–π‘’π‘š)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝑀𝑔𝑆𝑂4
1(24
...
37 𝑔/π‘šπ‘œπ‘™ x100
24
...
37𝑔/π‘šπ‘œπ‘™ x100
Percent Magnesium = (
...
2%
Percent Sulfur
𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π‘†π‘’π‘™π‘“π‘’π‘Ÿ)

Percent Sulfur = π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝑀𝑔𝑆𝑂 x 100
4
1(32
...
37 𝑔/π‘šπ‘œπ‘™ x100
32
...
37𝑔/π‘šπ‘œπ‘™ x100
Percent Sulfur = (
...
6%
Percent Oxygen
Percent Oxygen =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝑂π‘₯𝑦𝑔𝑒𝑛)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝑀𝑔𝑆𝑂4
4(16
...
37 𝑔/π‘šπ‘œπ‘™ x100
64
...
37𝑔/π‘šπ‘œπ‘™ x100
Percent Oxygen = (
...
2%
Magnesium sulfate (MgSO4) is composed of 53
...
6% Sulfur and 20
...
Dela Cruz

Study Guide

3
...
07 g/mol
12
...
00 g/mol
Molar mass of CaCO3

1
1
3

Total mass
contributed by the
element
40
...
01 g/mol
48
...
08 g/mol

Percent Calcium
Percent Calcium =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ πΆπ‘Žπ‘™π‘π‘–π‘’π‘š)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ πΆπ‘ŽπΆπ‘‚3
1(40
...
08 𝑔/π‘šπ‘œπ‘™ x100
40
...
08𝑔/π‘šπ‘œπ‘™ x100
Percent Calcium = (
...
0%
Percent Carbon
Percent Carbon =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ πΆπ‘Žπ‘Ÿπ‘π‘œπ‘›)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ πΆπ‘ŽπΆπ‘‚3
1(12
...
08 𝑔/π‘šπ‘œπ‘™ x100
12
...
08𝑔/π‘šπ‘œπ‘™ x100
Percent Carbon = (
...
0%
Percent Oxygen
Percent Oxygen =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝑂π‘₯𝑦𝑔𝑒𝑛)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ πΆπ‘ŽπΆπ‘‚3
3(16
...
08 𝑔/π‘šπ‘œπ‘™ x100
48
...
08𝑔/π‘šπ‘œπ‘™ x100
Percent Oxygen = (
...
0%
Calcium carbonate (CaCO3) is composed of 48% Oxygen, 12% Carbon, and 40% Calcium by
mass
...
Dela Cruz

Study Guide

4
...
01 g/mol
1
...
03 g/mol
8
...
03 g/mol

Percent Carbon
Percent Carbon =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ πΆπ‘Žπ‘Ÿπ‘π‘œπ‘›)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝐢3 𝐻8
3(12
...
03 𝑔/π‘šπ‘œπ‘™ x100
36
...
03𝑔/π‘šπ‘œπ‘™ x100
Percent Carbon = (
...
8%
Percent Hydrogen
Percent Hydrogen =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π»π‘¦π‘‘π‘Ÿπ‘œπ‘”π‘’π‘›)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝐢3 𝐻8
8(1
...
03 𝑔/π‘šπ‘œπ‘™ x100
8
...
03𝑔/π‘šπ‘œπ‘™ x100
Percent Hydrogen = (
...
2%
Propane (C3H8) is composed of 18
...
8% Carbon
5
...
10 g/mol
54
...
00 g/mol
Molar mass of CaCO3

1
1
4

Percent Potassium
Percent Potassium =

𝑛(π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ π‘ƒπ‘œπ‘‘π‘Žπ‘ π‘ π‘–π‘’π‘š)
x 100
π‘šπ‘œπ‘™π‘Žπ‘Ÿ π‘šπ‘Žπ‘ π‘  π‘œπ‘“ 𝐾𝑀𝑛𝑂4
1(39
...
04 𝑔/π‘šπ‘œπ‘™ x100
39
...
04 𝑔/π‘šπ‘œπ‘™ x100
Percent Potassium = (
...
7%
8

Reymon T
...
10 g/mol
54
...
00 g/mol
158
...
94𝑔/π‘šπ‘œπ‘™)

Percent Manganese = 158
...
94 𝑔/π‘šπ‘œπ‘™

Percent Manganese = 158
...
348) x100
Percent Manganese = 34
...
00𝑔/π‘šπ‘œπ‘™)

Percent Oxygen = 158
...
00 𝑔/π‘šπ‘œπ‘™

Percent Oxygen = 158
...
405) x100
Percent Oxygen = 40
...
5% Oxygen, 34
...
7%
Potassium
...
Dela Cruz


Title: Percent composition of compounds
Description: This material deals with learning how to determine the percent composition of compounds. It outlines in detail the procedures for arriving at the correct percent composition.