Learning Goals
0 Explain how a mole is used to
indirectly count the number of
particles of matter.
0 Relate the mole to a common
everyday counting unit.
0 Convert between moles and number
of representative particles.
Counting Particles
0 Chemists need a convenient
method for accurately counting
the number of atoms, molecules,
or formula units of a substance.
0 The mole is the SI base unit used to
measure the amount of a
substance.
Counting Particles
0 1 mole is the amount of atoms in 12
g of pure carbon-12, or 6.02 x 1023
representative particles
0 an atom, a molecule, a formula unit,
an electron, an ion, etc.
0 The number is called Avogadro’s
number.
Counting Particles
0 This relationship allows us to count
atoms by weighing them.
Counting Particles
0 Twenty-two real copper pennies
contain about 1 mol of copper (Cu)
atoms.
Counting Particles
0 Two large helium
balloons contain
approximately 1 mol
of helium (He) atoms.
Converting Between Moles and Particles
0 Moles to particles:
Converting Between Moles and Particles
0 Example: How many atoms are in
3.50 mol of He?
Converting Between Moles and Particles
0 Particles to moles
Converting Between Moles and Particles
0 Example: If there are 1.1 x 1022 Ag
atoms, how many moles of Ag are
there?
Practice
0 Calculate the number of molecules
in 11.5 mol of water.
Practice
0 How many moles are in 5.75 x 1024
atoms of aluminum?
Practice
0 How many molecules of AgNO3 are
there in 3.25 mol of AgNO3? How
many atoms are there?