Unit 1 continued The Mole!!!
Jan 20, 2016
Unit 1 continuedThe Mole!!!
Intro to the Mole
Counting by Mass
The Mole
Molar Mass
Counting Candy: Counting by Mass Sometimes it is inconvenient or even impossible to
count using traditional methods
Small particles
Large numbers of particles
Counting by mass uses the average mass of the particle to calculate a given number of particles
How much candy is in my jar?
Get an average mass (massA)
Get a total mass (masst)
# particles = masst/massa
Atomic Masses and the Mole
You can calculate the given number of atoms using the atomic mass
Atomic mass is the weighted average mass of all the isotopes of an atom
Atomic mass expressed in AMU’s is the mass of 1 atom of that element
The atomic mass expressed in grams is the mass of 1 mole of atoms
…So, what is a mole?
The Mole
Suppose we have a sample of Al with a mass of 26.98g
What mass of Cu would have the same number of atoms?
How about C?
If we were to measure out samples of any elements such that the masses in grams are equal in number to the atomic masses, we will ALWAYS have the same number of atoms!
THAT NUMBER IS CALLED…THE
MOLE!
More Mole
The Mole: the number equal to the number of carbon atoms in 12.01g of carbon. It is associated with a specific number:
Avogadro's Number
6.022x1023 of anything is a mole
Think “dozen”
It is a UNIT!
Molar Mass = mass of 1 MOLE
Element: The molar mass of an element is equal to the atomic mass expressed in grams instead of AMU’s
What is the Molar Mass of
Carbon
Nickel
Oxygen (careful diatomic!)
Compound: The molar mass of a compound is equal to the sum of the molar masses of each element in the compound in the correct ratio.
Calculate the molar mass of:
CO2
NaCl
Pb2(SO4)3
Picture of Molar Mass
A little help please (mole problem flow chart)
Practice!
Calculate the Number of particles (atoms/molecules) in:
2.5 mols Na
76 g K
23 g CO2
1240 mg HBr
Calculate the mass of:
1.0 mols CH4
6.022x1023 atoms of Na
2.4 mols PbNO3
2.3x1022 mlcs H2SO4
More Practice!
Calculate the molar mass of the following:
Molybdenum
Lanthanum
CBr4
HgO
TiO2
MnCl2
PH3
Perform the following calculations:
1.0 moles O2 particles O2
2.6 g Cu moles Cu
4.0x1022 atoms Al moles Al
4.0x1022 atoms Al grams Al
26.2g NaCl moles NaCl
26.2 g NaCl particles NaCl
End the Mole Madness!
Tips to help with mole problems…
In the conversion process, the mole gets a 1
6.022x1023 will ALWAYS be atoms, particles, etc.
Use the molar mass any time you see grams
Let your units tell the story