1. Avogadro’s Number Mole Molar Mass
Measuring Matter
Avogadro’s Number
Mole
Molar Mass

2. How Scientists Keep Track of Atoms
A ream of paper is 500 sheets:
1 ream = 500 sheets
A counting unit appropriate for objects based on their size/function
Always constant
Easier to sell by ream than by sheet
Scientist could count atoms
Atoms are extremely small
The number of individual particles even in a small sample is REALLY SMALL!

3. The Mole A ‘chemical’ counting unit SI base unit
Measures amount of a pure substance
Abbreviated ‘mol’
Scientist developed
One mole contains Avogadro’s number of particles
This number is named in honor of Amedeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter the identity of the gas, there were the same number of molecules present

4. How much is the mole? Similar to a dozen except instead of 12,
A mole = or 6.02 x 1023 = Avogadro’s Number.
It is equal to that number no matter what kind of particles:
Atoms
Molecules
Formula unit

5. How Do We Use The Mole?
We’d never use the mole to describe macroscopic or real world objects.
1 mole (6.02x1023) of watermelon seeds would be found inside a watermelon the size of the moon.
1 mole (6.02x1023) of donut holes would cover the earth and would be 5 miles deep.

6. How do we use the mole? Mole is a huge number of particles
only used to describe the amount of things that are very, very small.
1 mole (6.02x1023) of water molecules would barely fill a shot glass

7. A Mole of Particles Contains 6.02 x 1023 particles
= 6.02 x 1023 C atoms = 6.02 x 1023 H2O molecules = 6.02 x 1023 NaCl formula units
1 mole C
1 mole H2O
1 mole NaCl

8. Avogadro’s Number as Conversion Factor
6.02 x 1023 particles
1 mole or
1 mole
Note: a particle could be an atom, a molecule or a formula unit

9. Practice How many moles of silver are in 3.01x1023 atoms of silver?
Given:
3.01 x 1023 atoms Ag
Find:
Moles of Ag
6.02x1023 atoms = 1 mol Ag
3.01x1023 Ag atoms
1 mol Ag
6.02x1023 Ag atoms
= 0.500mol Ag
= 0.5 mol Ag

10. Molar Mass The mass of one mole of a pure substance UNIT: (g/mol)
Equal to the numerical value of the average atomic mass (PT)
1 mole of C atoms = g
1 mole of Mg atoms = g
1 mole of Cu atoms = g

11. Other Names Related to Molar Mass
Molecular Mass/Molecular Weight
Formula Mass/Formula Weight:
THE POINT: You may hear all of these terms which mean the SAME Number from the periodic table!!

12. Learning Check! = 79.90 g 1 mole of Br 1 mole of Sn = 118.71 g
Find the molar mass
= g
1 mole of Br
1 mole of Sn
= g
Learning Check!

13. Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses
1 mole of CaCl2 =
1 mole Ca x g/mol
+ 2 moles Cl x g/mol = g/mol
1 mole of N2O4
g CaCl2
= g

14. Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 =

15. Learning Check! Molar Mass of K2O = ______ g/mol
Molar Mass of N2O4 = _______g/mol
Molar Mass of H20 = ______ g/mol

16. Calculations with Molar Mass
Grams Moles
Calculations with Molar Mass

17. Practice 9.60 mol Al G: F: 1 mol Al = 26.98 g g of Al
Aluminum is often used for the structure of light- weight bicycle frames. How many grams of Al are in 9.60 moles of Al? G: F:
9.60 mol Al
1 mol Al = g
g of Al

18. Practice G: F: 9.60 mol Al 1 mol Al = 26.98 g g of Al 9.60 mol Al
Aluminum is often used for the structure of light- weight bicycle frames. How many grams of Al are in 9.60 moles of Al? G: F:
9.60 mol Al
1 mol Al = g
g of Al
9.60 mol Al
26.98 g Al
= 259 g Al
1 mol Al

19. Practice
Propane gas is needed to operate gas grills. Your father used grams of propane to grill burgers over the weekend. How many moles of propane did he use up? Propane = C3H8 G: F:
110.6 g C3H8
1 molC3H8 = g
mol of C3H8

20. Practice
Propane gas is needed to operate gas grills. Your father used grams of propane to grill burgers over the weekend. How many moles of propane did he use up? Propane = C3H8 G: F:
110.6 g C3H8
1 molC3H8 = g
mol of C3H8
110.6 gC3H8
1 mol C3H8
= mol C3H8
44.11 g C3H8

21. Calculations using Molar Mass & Avogadro’s Number
Remember: There may not always be a direct pathway to the final answer!!
molar mass Avogadro’s number Grams Moles particles
Calculations using Molar Mass & Avogadro’s Number

22. The TWO Step – I Work it Out!!
How many atoms of Cu are present in 35.4 g of of copper?
1 mol Cu = g G: F:
35.4 g Cu
1 mol Cu = 6.02 x 1023 atoms
atoms of Cu
35.4 g Cu
1 mol Cu
6.02 x 1023 atoms Cu
63.55 g Cu
1 mol Cu
= 3.35 X 1023 atoms Cu
molar mass Avogadro’s number Grams Moles particles

23. The TWO Step – I Work it Out!!
How many atoms of Cu are present in 35.4 g of of copper?
1 mol Cu = g G: F:
35.4 g Cu
1 mol Cu = 6.02 x 1023 atoms
atoms of Cu
molar mass Avogadro’s number Grams Moles particles

24. Learning Check!
What is the mass (in grams) of 1.20 X molecules of glucose (C6H12O6)?
molar mass Avogadro’s number Grams Moles particles

25. Now you work it out!
How many atoms of O are present in 78.1 g of oxygen?
78.1 g O2 1 mol O X 1023 molecules O2 2 atoms O g O mol O molecule O2