we frequently refer to measures casually… couple few dozen baker’s dozen ream lord 2 3 12 13 500...
TRANSCRIPT
A Chemist’s Dozen
Common MeasuresWe frequently refer to measures casually…
Couple
Few
Dozen
Baker’s Dozen
Ream
LORD
2
3
12
13
500
4
Atoms are REALLY small!!! We can’t work with individual atoms or
atomic mass units in the LAB – Because we can’t see things that small
we work with samples large enough for us to SEE and WEIGH on a balance using units of grams.
This Creates a Problem…
Billions of atoms are hard to keep track of in calculations
A pile of atoms big enough for us to see contains billions of atoms.
A Chemist’s Dozen
It represents a number of ‘things, just like a dozen
In honor of Amedeo Avogadro, Italian chemist (1776-1856)
6.022 x 1023 is referred to as
Avogadro’s Number (NA)
1 mole (unit: mol) = 6.02 x 1023 atoms(symbol: n) (or molecules)
The Mole (n)
This is a HUGE number!!!!
1 mole = 6.02 x 1023 particles, molecules, atoms.
1 dozen eggs = 12 Eggs
1 mole of eggs = 6.02 x 1023 Eggs
How Big is a Mole?
A mole of marbles would cover the entire Earth’s surface 50 MILES DEEP!!!!
How Big is a Mole? If you spent a BILLION DOLLARS
every SECOND, you couldn’t spend a mole of dollar bills in your lifetime!!!
How Big is a Mole? If you were able to count at the rate
of 1 million numbers a second, it would take about 20 billion years to count out one mole.
What are particles?Molecules – covalently
bonded compounds. Usually a non-metal and a non-metal.
The molecule of water is the particle that is counted.
1 mole of water has 6.02 x 1023 molecules/mol.
What are particles?Formula Units– ionically
bonded compounds. Usually a metal and a non-metal
The formula unit of salt is the particle that is counted
1 mole of salt has 6.02 x 1023 formula units/mol
What are particles?Atoms– elemental.Found on the PT of E,
but not part of HOFBrINCl.
The atom of copper is the particle that is counted.
1 mole of copper has 6.02 x 1023 atoms/mol
Pop QuizIdentify the unit for each substance.
a) Methane (CH4)
b) Magnesium chloride
c) Aluminum
d) Butane (C4H10)
e) Hydrogen peroxide
f) Sodium nitrate
g) Calcium
a) moleculeb) F.U.c) atomsd) moleculee) moleculef) F.U.g) atoms
Moles to Particles Calculations
A “dozen” is an easy way to say “12”.
A “mole” is an easy way to say “6.02 x 1023”
Calculation Line
MOLE Particles(molecules F.U. Atoms)
X
÷
Avogadro’s Number
There are 0.50 mol of methane, CH4 in a flask. How many
molecules are present?
N = n x NA
= (0.50 mol)(6.02 x 1023 molecules/mol)
= 3.01 x 1023 molecules
There are 3.01 x 1023 molecules of methane
How many molecules are found in 1.25 mol of CO2?
N = n x NA
= (1.25 mol)(6.02 x 1023 molecules/mol)
= 7.525 x 1023 molecules
There are 7.52 x 1023 molecules of carbon dioxide.
How many moles are found in 5.83 x 1024 molecules of CO2?
n = N/NA
= 5.83 x 1024 molecules 6.02 x 1023 molecules/moln = 9.68 mol
Therefore there are 9.68 mol.
How many moles are found in 3.57 x 1025 atoms of zinc?
n = 3.57 x 1025 atoms 6.02 x 1023 atoms/moln = 59.3 mol
Therefore there are 59.3 mol of zinc.