• Chemistry is a quantitative science - we need a "counting unit."
• The MOLE
• 1 mole is the amount of substance that contains as many particles (atoms or molecules) as there are in 12.0 g of C-12.

[2 x 1] 2 amu 1
Avogadr oPaper
Carbon Atoms
Number Mass (amu)
Hydrogen Atoms
Number Mass (amu)
1
Mass Ratio
Mass carbon / Mass hydrogen
12 amu = 12
1 amu 1
12
24
[2 x 12]
120
[10 x 12] [10 x 1] 10 amu 1
600
[50 x 12]
[50 x 1]
50 amu 1
Avogadro’s number
(6.02 x 10 23 ) x (12)
Avogadro’s number (6.02 x 10 23 ) x (1)
(6.02 x 10 23 ) x (12) = 12
(6.02 x 10 23 ) x (1) 1

Particles in a Mole
Amedeo Avogadro (1766-1856)
(1776 – 1856) it was named in his honor by a
French scientist in 1909. its value was first estimated by Josef Loschmidt, an Austrian chemistry teacher, in 1895
.
?
quadrillions trillions billions millions thousands
1 mole = 602213673600000000000000 or 6.022 x 10 23
There is Avogadro's number of particles in a mole of any substance.

Q: How much is a mole?
A: A mole is a quantity used by chemists to count atoms and molecules. A mole of something is equal to 6.02 x 10 23 “somethings.”
1 mole = 602 200 000 000 000 000 000 000
Q: Can you give me an example to put that number in perspective?
A: A computer that can count 10,000,000 atoms per second would take 2,000,000,000 years to count 1 mole of a substance.

Is that right? A computer counting 10 million atoms every second would need to count for 2 billion years to count just a single mole .
Lets look at the mathematics.
x sec = 1 year
365 days
1 year
24 hours 60 min
1 day 1 hour
60 sec
1 min
= 31,536,000 sec
Therefore 1 year has 31,536,000 seconds or 3.1536 x 10 7 sec.
A computer counting 10,000,000 atoms every second could count
3.153 x 10 14 atoms every year.
Finally, 6.02 x 10 23 atoms divided by 3.1536 x 10 14 atoms every year equals 1,908,929,477 years or approximately 2 billion years!

One mole of marbles would cover the entire Earth
(oceans included) for a depth of three miles.
One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 million times.
It would take light 9500 years to travel from the bottom to the top of a stack of 1 mole of $1 bills.

 A MOLE of any substance contains as many elementary units
(atoms and molecules) as the number of atoms in 12 g of the isotope of carbon-12.
 This number is called AVOGADRO’s number N
A particles/mol
= 6.02 x 10 23
 The mass of one mole of a substance is called MOLAR MASS symbolized by MM
 Units of MM are g/mol
 Examples
H
2
He
N
2
O
2
CO
2 hydrogen helium nitrogen oxygen carbon dioxide
2.02 g/mol
4.0
28.0
32.0
44.0 g/mol g/mol g/mol g/mol

• You have 98.4g of Na. How many moles of Na do you have in sample?
• You have 127g of CO2 in sample. How many moles of CO2 do you have?
• 7.2 moles of Ca is equal to how many grams of Ca?

• The reactant in a chemical reaction that limits the amount of product that can be formed. The reaction will stop when all of the limiting reactant is consumed.

• Excess Reactant - The reactant in a chemical reaction that remains when a reaction stops when the limiting reactant is completely consumed. The excess reactant remains because there is nothing with which it can react.

• A 50.6 g sample of Mg(OH)2 is reacted with 45.0 g of HCl according to the reaction:
• Mg(OH)2 + 2 HCl --> MgCl2 + 2 H2O
• What is the yield of MgCl2?

• The theoretical yield is the maximum amount of product which can be produced
(in an ideal world). In the "real" world it is difficult to produce the amount obtained for the theoretical yield. A percent yield is often used to show how close to ideality one has obtained in a chemical synthesis.

• Experimentally the chemist found that
46.5g of NaCl was collected at the end of the experiment. However in his calculations he found that he should have produced 50g of NaCl. What was his percentage yield?

• Given the reaction:
• 2H + O  H2O
• In this reaction you have 16 grams of both
H and O. After the reaction you collected16.98 grams H2O what is your percentage yield?

• NH3 + O2 → NO + H2O
• Assuming you had 43 grams of NH3 and
23 grams O2. You actually collected 71.23 grams of NO. What was your percentage yield of NO?