Download Unit 7 - Mole Conversions (Chapter 3 section 3 Chapter 11 section 3

Unit 7 - Mole Conversions
(Chapter 3 section 3 Chapter 11 section 3)
The Mole
 A counting unit
 1 mole = 602,214,150,000,000,000,000,000
= 6.022 X 1023 (in scientific notation)
 Also called Avogadro’s number
Just How Big is a Mole?
 Enough soft drink cans to cover the surface of the earth to a depth of over 200
miles.
 It would take over 19 million years to spend Avogadro's number of dollars if
the money were spent at the rate of one billion dollars per second.
 .If we were able to count atoms at the rate of 10 million per second, it would
take about 2 billion years to count the atoms in one mole.
Learning CheckT
Suppose we invented a new collection unit called a rapp. One rapp contains 8
objects.
1) How many paper clips in 1 rapp?
a) 1
b) 4
c) 8
2) How many oranges in 0.56 rapp?
a) 4
b) 8
c) 16
3) How many rapps contain 47 gummy bears?
a) 5
b) 10
c) 20
1) 1 mole C
= 6.022 x 1023 ___ atoms
2) 1 mole H2O = ___________H2O molecules
3) 1 mole H2O = ___________atoms
4) 1 mole NaCl
= 6.022 x 1023 NaCl __________
5) 1 mole NaCl
= __________ ions
The Mole
1 dozen cookies = 12 cookies
1 mole of cookies = 6.022 X 1023 cookies
1 dozen cars = 12 cars
1 mole of cars = 6.022 X 1023 cars
1 dozen Al atoms = 12 Al atoms
1 mole of Al atoms = 6.022 X 1023 atoms
Note that the NUMBER is always the same, but the MASS is very different!
Representative Particles
The smallest unit of the material that retains the properties of that material
 Element 
 Covalent compound
 Ionic compound


What exactly is a formula unit?
Mole  Molecule
1 mole H2O
= _________ H2O molecules
1 mole H2O
= _________ atoms
1 H2O molecule
= _________ atoms
Avogadro’s Number as Conversion Factor
6.02 x 1023 particles
1 mole
or
1 mole
6.02 x 1023 particles
Examples
How many moles of magnesium is 3.01 x 1022 atoms of magnesium?
How many molecules are there in 4.00 moles of glucose, C6H12O6?
How many atoms are in 0.750 moles of zinc?
How many atoms are in 4 molecules of C6H12O6?
What are the representative particles of chlorine gas and how many are there in 1.24
mole?
How many atoms of Cl are in 1.24 mole of chlorine gas?
What is the number of ions in 3 moles of Ca(NO3)2?
How many ions are in 3 formula units of Ca(NO3)2?
How many moles of ions are in 3 moles of Ca(NO3)2?
Molar Mass
•
The Mass of 1 mole (in grams)
– Can also be called
• atomic mass
• molecular mass
• formula mass
(mole of
(mole of
mole of
1 mole of C = 6.022 X 1023 C atoms
= 12.01 g
1 mole of Al = 6.022 X 1023 Al atoms
= _________ g
1 mole of Ne = __________ Ne atoms = _________ g
Molar Mass of Compounds
What is the molar mass of:
CaCl2
N2O4
K2O
Al(OH)3
CuSO4 . 5H2O
)
)
)
Oxygen gas
Molar Mass as conversion factor
g
1 mole
or
1 mole
g
Examples
How many mole are in 333 g SnF2
15.0 mol H2SO4 is equal to how many grams?
847 g (NH4)2CO3 converted to moles
2.40 mol nitrogen gas has what mass.
Molar Volume
At standard temperature and pressure(STP, 0 °C and 1 atm) 1 mole of any gas will
occupy 22.414 L (or 22.414 dm3)
Molar Volume as Conversion Factor
22.4 L
1 mole
or
1 mole
22.4 L
Examples
5.40 mol O2 occupies what volume.
89.6 L Ne is how many mole?
Now let’s move on to two step mole conversions
Examples
How many atoms of K are in 78.4 g of K?
What is the mass of 1.20 X 1024 molecules of glucose (C6H12O6)?
How many atoms of O are present in 78.1 L of oxygen?
Find the mass of 18.0 L of CH4
Find the mass of one atom of nickel.
Find the number of molecules in 60.0 g of N2O.
Percent Composition
% composition =
mass due to specific element
X 100
molar mass of compound
Examples
Find the percent of C in CO2
Find the percent mass of oxygen in Al3(PO4)2
Types of Chemical Formulas
Empirical Formula
 The formula of a compound that expresses the smallest whole number
ratio of the atoms present.
 Ionic formula are always empirical formula
Molecular Formula
 The formula that states the actual number of each kind of atom found in
one molecule of the compound.
If C6H12O6 is the molecular formula, what is the empirical formula?
What is the empirical formula for N2O10?
What is the empirical formula for N2O5?
A molecular formula is a multiple of the empirical formula.
To obtain an Empirical Formula
1.
Determine the mass in grams of each element present, if necessary.
2.
Calculate the number of moles of each element.
3.
Divide each by the smallest number of moles to obtain the simplest whole
number ratio.
If whole numbers are not obtained* in step 3), multiply through by the smallest
number that will give all whole numbers
*
Be careful! Do not round off numbers prematurely
Examples
A sample of a brown gas is found to contain 2.34 g N and 5.34g O. Determine the
empirical formula for this substance.
Calculate the empirical formula
57.14 g C, 6.16 g H, 9.52 g N, 27.18 g O
A sample of copper metal weighing 2.50 g is heated to form an oxide of copper. The
final mass of the oxide is 3.13 g. Determine the empirical formula of the oxide.
What is the empirical formula lactic acid if the percent composition is 40.00% C,
6.71% H, 53.29% O?
Calculation of the Molecular Formula
A molecular formula is a multiple of the empirical formula.
A compound has an empirical formula of NO2. The molecular mass is 92.0 g/mole.
What is the molecular formula of this substance?
If lactic acid has a molar mass of 90 g/mole, what is the molecular formula?