Mole Conversion
Homework
1) 1.39 moles H2O
8) 220g CaCl2
2) 134.1 g Li2O
9) 72g HCl
3) 1.38x1025 molecules O2
10) 11.4 g O2
4) 0.56 moles H2SO4
11) 2.8x10-21 moles Ca
5) 8.85x1023 molecules NH3
12) 56L H2
6) 106.7 g N2I6
7) 5.7x1022 molecules KMnO4
Percent Composition
 What percentage of an element is in a chemical
compound?
 Part x 100
Whole
 Use Formula Mass
 Percent mass of an element—
 Mass of an element in 1 mole of a chemical compound
Example 1:
Find the percent composition of hydrochloric acid (HCl).
Example 2:
 Find the percent by mass of magnesium, carbon, and
oxygen in magnesium carbonate.
Example 3:
 The formula for DDT is C14H9Cl5. What is the percent
by mass of carbon, hydrogen, and chlorine in this
compound?
Example 4:
 Osteoporosis is a disease caused by low calcium levels
in diets. Calcium tablets can be supplements to diets
and are either calcium carbonate, calcium sulfate, or
calcium phosphate. Based on the percent by mass of
calcium in each chemical compound, which tablet is
the most efficient dietary supplement for calcium
levels?
Practice
1) Calculate the mass of zinc in a 30.00g sample of zinc
nitrate, Zn(NO3)2
2) Calculate the mass of silver in 325g of silver cyanide
(AgCN)
3) What is the percentage of bromine in calcium bromide
(CaBr2)?
4) What is the percent composition of sodium carbonate,
Na2CO3?
Homework
 Percent Composition Worksheet