Chemistry Quarter 2

2. Module 4: What’s in a MOLE
1. How is the mole used to express the mass of a
substance?
2. How is the percentage composition of a given compound
determined?
Objectives:
• use the mole concept to express mass substances; and
• Determine the percentage composition of a compound
given its chemical formula and vice versa

3.  Given the SI symbol mol and is equivalent to
Avogadro’s number, 6.02X1023 particles
 Particles can be atoms, molecules, or formula units.
 One mole of different substances always contains
6.02X1023 particles but each of these substances has a
different mass
 Lorenzo Romano Amedeo Carlo Avogadro (1776-1856), Italian
scientist
 First suggested that it might be possible to count atoms
 Established a law stating that equal volumes of gases contain
the same number of molecules at the same temperature and
pressure.
MOLE

4. The interconversion of mass, mole, and number of particles of an element
mass No. of
moles
No. of
particles
Divide by
Molar mass
Multiply by
Multiply by
Avogadro’s #
Divide by

5. MATTER
Particles
Avogadro’s #
A mole g/mol
molecules
ions
atoms
Is made up of
W/c may be
Whose amount may be expressed in terms of
Whose mass is
expressed in
Equal to

6. Percentage composition of a Compound
 The mass of each element in a compound compared to
the entire mass of the compound multiplied by 100
percent
 Tells the percentage of the mass made up by each element
in a compound
% composition = mass of component element X 100
mass for molar mass of compound