Molar Mass & Conversions
The Mole
mole (mol)- SI Unit for
the amount of a
substance that
contains as many
particles as there are
atoms in exactly 12g
of carbon-12.
• A unit of counting,
like the dozen.
Avogadro’s Number
Avogadro’s Number - the number of particles in
exactly one mole of a pure substance.
1 mole = 6.0221415 X
1 mol = 6.022 x
23
10
Amedeo Avogadro
23
10
Atomic Mass
atomic mass - the mass of one mole of an atom
• Atomic mass is expressed in atomic mass units
(amu) or (u) or g/mol.
• Can be found on the periodic table.
• All atomic masses are based on the atomic mass
of carbon-12 being 12 amu.
Molar Mass
molar mass - the mass of one
mole of a pure substance.
•Molar mass is written in units
of amu or g/mol.
Atomic mass vs. Molar mass
•atomic mass - the mass of one
mole of an atom.
•molar mass - the mass of one
mole of a pure substance.
Atomic Mass vs. Molar Mass
Example
Atomic Mass
Molar Mass
Na
22.99 g/mol
22.99 g/mol
Ag
107.87 g/mol
107.87 g/mol
C
12.01 g/mol
12.01 g/mol
O
16.00 g/mol
16.00 g/mol
Molar Mass of Compounds
Compound
H2O
C6H12O6
Molar Mass
18.02 g/mol
180.18 g/mol
NaCl
58.44 g/mol
Cl2
70.90 g/mol
(NH4)3PO4
149.12 g/mol
CuSO4·5H2O
249.72 g/mol
Introduction to Molar Conversions
Amount
Mass
1 mol O2
32.00 g
½ mol O2
16.00 g
2 mol O2
64.00 g
3 mol O2
96.00 g
Grams to Moles
Converting grams to moles: divide by molar mass.
1. How many moles of Ca are in 5.00g of Ca?
1 mol Ca
5.00g Ca x
= 0.125 mol Ca
40.08 g Ca
2. How many moles of H2O are in 36.0g of H2O?
1 mol H 2 O
36.0 g H 2 O x
=
18.02 g H 2 O
2.00 mol H 2O
3. How many moles of AgNO3 are in 124.5g of AgNO3?
1 mol AgNO3
124.5 g AgNO3 x
= 0.7329
169.88 g AgNO3
mol AgNO3
Moles to Grams
Converting from moles to grams: multiply by molar
mass.
1. What is the mass in grams of 2.25
moles of Fe?
55.85 g Fe
2.25 mol Fe x
= 126 g Fe
1 mole Fe
2. What is the mass in grams of 0.896
moles of BaCl2?
187 g BaCl2
Types of Particles
• Atoms – C, Cu, He
• Molecules – O2, C12H22O11, CO2 (all nonmetals in
the formula)
• Formula units – NaCl, CaCl2, Mg(NO3)2
(includes a metal in the formula)
Particles
to Moles
Converting particles
to moles:
divide by
Avogadro's Number.
1.
How many moles of Pb are in 1.50 X 1025
atoms of Pb?
2.49 x 101 moles Pb
2. How many moles of CO2 are in 6.78 X 1021
molecules of CO2?
1.13 x 10-2 moles CO2
Moles
to Particles
Converting moles
to atoms:
multiply by
Avogadro's Number.
1.
How many molecules of NO are in 0.87 moles
of NO?
5.2 x 1023 molecules NO
2. How many formula units of NaI are in 2.50
moles of NaI?
1.51 x 1024 formula units NaI
Grams to Moles to Particles
Example: How many molecules of N2
are in 57.1g of N2?
23
1 mol N 2
6.02
x
10
molecules
N
2
57.1 g N 2 x
x
28.02 g N 2
1 mol N 2
= 1.23 x 1024 molecules N 2
Particles to Moles to Grams
Example: How many grams of NaF are
in 7.89 X 1024 formula units of NaF?
24
7.89 x 10 f.un. NaF x
1 mol NaF
6.02 x 1023 f.un. NaF
41.99 g NaF
x
1 mol NaF
= 550. g NaF
Atoms to Moles to Grams
Tough Example:
How many total atoms are in 235 g of CO2?
9.64 x 1024 total atoms
The Mole Bridge