Mole-Mass Relationship
The Mole Review
What is a mole?
How do scientists use the concept of the mole?
Who was the first person to come up with the
idea of the mole?
Molar Mass
• The atomic mass of an element expressed in
grams is the mass of 1 mole of that element.
• This is known as the element’s molar mass
(the mass of 1 mole)
How could we find the molar mass of a
compound ?
Finding Molar Mass of Compound
Step 1: Obtain chemical formula
Step 2: Add up all individual molar masses
Step 3: add unit (grams per mole)
Sample Problems in Molar Mass
The decomposition of hydrogen peroxide (H2O2)
provides sufficient energy to launch a rocket.
What is the molar mass of hydrogen peroxide?
Find the molar mass of PCl3.
What is the mass of 1 mol of sodium hydrogen
carbonate?
Mole-Mass relationship
• We can use the molar mass of a substance as
a conversion factor between moles and mass
of any substance.
Review: What is a conversion factor?
Example
The molar mass of NaCl is 58 g/mol
So the mass of 3 mol of NaCl can be found in the
following way:
3 mol NaCl X 58 g = 176 g
1 mol
Sample Problems
The aluminum Satellite dishes are resistant to
corrosion because the aluminum reacts with
oxygen in the air to form a coating of
aluminum oxide. This tough, resistant coating
prevents any further corrosion. What is the
mass of 9.45 mol of aluminum oxide?
Sample Problems
Find the mass, in grams, of 0.00045 mol of
C20H42.
Calculate the mass, in grams, of 2.5 mol of iron
(III) hydroxide.
Mole-Particle Relationship
We can convert between moles of a
compound/substance and the number of
particles in that substance.
By Particles we mean…
– Atoms
– Molecules/compounds
Sample Problems
Find the number of molecules in a 75 g sample
of dinitrogen trioxide.
Find the number of atoms of gold in 2 mol of
gold.