PERCENT COMPOSITION

1
PERCENT COMPOSITION

• The percent composition is the mass percentage of
  each type of atom(element) in a compound.
• X (total atomic mass of X / molar mass which
  contains X)
• For Example
• Calculate the percent composition of nicotine,
  C10H14N2.
• Molar mass 10C 14H 2N 162 g/mol
• C (10C / C10H14N2)100 (120 g/mol /162
  g/mol)10074.1
• H (14H / C10H14N2)100 (14 g/mol / 162
  g/mol)100 8.6
• N (2 N / C10H14N2)100 (28 g/mol / 162
  g/mol)100 17.3

2
PERCENT COMPOSITION

• The percent composition can also be calculated
  from experimental data.
• X (total mass of X / total mass of compound)
• A student prepares a compound of tungsten
  chloride from 3.946 g of tungsten and 3.806 g of
  chlorine. Assuming the reaction goes to
  completion, calculate the percent composition.
• According to the Law of Conservation of Mass,
  3.946 g of W combines with 3.806 g of Cl to give
  7.752 g of compound.
• W (mass W / mass WxCly )100 (3.946 g / 7.752
  g)100 50.9
• Cl (Cl / WxCly )100 (3.806g / 7.752 g)100
  49.1

3
PRACTICE PROBLEMS 11
A
_____1. A 45.9 g sample of Copper, Cu, combined
with oxygen to give 51.69 g of an oxide compound.
The percent composition of this compound
is a) 88.8 Ca, 11.2 O b) 24.4 Ca,
75.6 O c) 60.1 Ca, 39.9 O d) 11.3
Ca, 88.7 O 2. Calculate the percent
composition for each set? H2O H _____
O _____ H2O2 H _____ O _____
3. How many grams of sodium will combine with
567.0 g of sulfur to form Na2S?.
11.1 88.9
5.88 94.1
815.6 g