Download 1 mole = molar mass

Unit 2 Lesson #5
Avogadro’s Number
& The Mole (p.14-16)
How Big is A Mole?
A. What is the Mole?
1. A counting number (like a dozen)
2. Avogadro’s number (NA)
1 mole = 6.022  1023 representative particles
3. Using Dimensional Analysis to Make Conversions
a. Convert 48 eggs to dozens of eggs
Conversion factor :
48 eggs
1
X
1 dozen
12 eggs
X
12 eggs
1 dozen
b. Convert 6 dozen to number of eggs
Conversion factor :
6 dozen
1
4. Molar Conversion Factors
a. # of Particles (atoms, molecules, ions, etc.)
1 mole = 6.022  1023 particles
b. Molar mass = mass of 1 mole of a substance
1 mole = molar mass
c. Molar Volume = 22.4 Liters for any gas at STP
(Standard Temperature Pressure)
*STP = T = 0o C or 273 K P = 1.0 atmosphere (atm)
1 mole = molar volume
Mole Relationships
http://itschemistrytime.blogspot.com/2011_11_01_archive.html
Representative Particles & Moles
Substance
Chemical
Formula
Carbon
C
Nitrogen gas
N2
Calcium ion
Ca2+
Magnesium
fluoride
MgF2
Representative
Particle
Rep Particles
in 1.00 mole
6.02 x 1023
6.02 x 1023
Representative Particles & Moles
Substance
Chemical
Formula
Representative
Particle
Rep Particles
in 1.00 mole
Carbon
C
Atom
6.02 x 1023
Nitrogen gas
N2
Molecule
6.02 x 1023
Calcium ion
Ca2+
Ion
6.02 x 1023
Magnesium
fluoride
MgF2
Formula unit
6.02 x 1023
B. Mole to Particle Conversions
6.022  1023
NA
NUMBER
MOLES
OF
PARTICLES
(particles/mol)
NA atoms/mol
NA molecules/mol
Particles = atoms,
molecules, formula
units, ions, etc
1. How many molecules are in 2.50 moles of
C12H22O11?
2.50 mol
C12H22O11
6.02  1023
molecules
C12H22O11
1 mol
C12H22O11
= 1.51  1024
molecules
C12H22O11
2. If you have 2.23 x 1018 atoms of sodium, how
many moles is that?
2.23  1018 1 mole Na
atoms Na
6.02  1023
atoms Na
3.70 x 10-6
= moles Na
3. How many formula units is 3.75 moles of
calcium hydroxide?
6.02  1023
3.75
formula units
mol Ca(OH)2 Ca(OH)2
= 2.26  1024
1 mol Ca(OH)2 formula units
Ca(OH)2
C. Molar Mass Conversions
1. Molar Mass = The mass of one mole of an
element or compound

Atomic mass (on the PT) tells the...
mass of each atom (amu)
 grams per mole (g/mol)

2. Round to 2 decimal places
3. Molar Mass Examples
a. carbon
12.01 g/mol
b. aluminum
26.98 g/mol
c. zinc
65.39 g/mol
4. Molar Mass Examples
a. water
 H2O
 2(1.01) + 16.00 = 18.02 g/mol
b. sodium chloride
 NaCl
 22.99 + 35.45 = 58.44 g/mol
5. Molar Mass Examples
a. sodium bicarbonate
 NaHCO3
 22.99 + 1.01 + 12.01 + 3(16.00)
b. sucrose
= 84.01 g/mol
 C12H22O11
 12(12.01) + 22(1.01) + 11(16.00)
= 342.34 g/mol
6. Molar Mass Examples
a. magnesium hydroxide
 Mg(OH)2
 24.31 + 2(16.00) + 2(1.01)
= 58.33 g/mol
b. ammonium sulfate
 (NH4)2SO4
 2(14.01) + 8(1.01) + 32.06 +
4(16.00)
= 132.16 g/mol
D. Molar Mass Conversions
6.02  1023
NA
molar
mass
MASS
NUMBER
MOLES
IN
GRAMS
(g/mol)
OF
(particles/mol)
PARTICLES
Particles = atoms,
molecules, formula
units, ions, etc
NA atoms/mol
NA molecules/mol
1. How many moles of carbon atoms
are in 26 g of carbon?
26 g C 1 mol C
12.01 g C
= 2.2 mol C
2. Find the mass of 2.1  1024 molecules
of NaHCO3.
2.1  1024
Molecules
NaHCO3
1 mol
84.01 g
NaHCO3
NaHCO3
6.02  1023 1 mol
Molecules
NaHCO3
NaHCO3
= 290 g NaHCO3
3. How many atoms are in 22.5 grams
of potassium?
22.5 g K
1 mol K
6.02  1023
atoms K
39.10 g K 1 mol K
= 3.46 x 1023 atoms K
E. Molar Volume Conversions
NA
Molar Mass
Molar Vol
* Molar Volume = 22.4 Liters for any gas at STP
1.
What is the volume at STP of 4.00 g of
CH4?
4.0g X
1
1 mole
16 g
X 22.4 L = 5.6 L
1 mole
2. How many grams of He are present in
8.00 L of He at STP?
8.0 L X
1
1 mole X 4.0 grams
22.4 L
1 mole
= 1.4 g