1. The Mole

2. Representative Particles
Element (Atoms)
atomic mass—mass of an atom in atomic mass units (amu)
Average atomic mass—weighted average of all naturally occurring isotopes of the element (amu)
By definition:
1 atom 12C “weighs” 12 amu
On this scale
1H = amu
16O = amu

3. Molecular compound/Molecule (Molecule)
Molecular mass (or molecular weight)—sum of the atomic masses (in amu) in a molecule.
SO2 1S
32.07 amu 2O
+ 2 x amu
SO2
64.07 amu

4. Ionic compound (formula unit)
Formula mass—sum of the atomic masses (in amu) in a formula unit of an ionic compound
NaCl
1Na
22.99 amu
1Cl
amu
NaCl
58.44 amu

5. Mole SI base unit used to measure the amount of a substance
Used to measure large amounts of very small things
Discovered by Avogadro and named after him
NA= 6.022×1023 particles= 1 mol of substance
Pair = 2
Dozen = 12

6. Dimensional Analysis Examples
Given 4.25 mol of sodium chloride, determine the number of formula units?

7. Calculate the number of molecules in 12.6 mol of sulfur dioxide.

10. Mass of 1 mol of particles in grams
Molar Mass
Mass of 1 mol of particles in grams

11. atomic mass (amu) = molar mass (grams)
For any element
atomic mass (amu) = molar mass (grams)
1 atom of Li = 6.94 amu
1 mole Li atoms = 6.94 g of Li
For any ionic compound
formula mass (amu) = molar mass (grams)
1 formula unit NaCl = amu
1 mole NaCl f.u.’s = g NaCl
For any molecule
molecular mass (amu) = molar mass (grams)
1 molecule SO2 = amu
1 mole SO2 molecules= g SO2

12. Examples
Calculate the molar mass:
C8H11NO2
Magnesium phosphate

13. Dimensional Analysis with Mass
M = molar mass in g/mol
NA = Avogadro’s number

14. Calculate the mass in grams of 0.0450 moles of chromium.
Examples
Calculate the mass in grams of moles of chromium.

15. What is the mass of 4.35 moles of sulfuric acid?

16. Calculate the number of moles of 321 g of lead(II) chloride.

17. How many formula units are in 124 g of mercury(II) chloride?

19. Take out question 6 a & b

20. How many oxygen atoms are in 37.5 grams of sulfur trioxide?
*bonus
How many oxygen atoms are in 37.5 grams of sulfur trioxide?

21. Molar Volume
The conditions 0 0C and 1 atm are called standard temperature and pressure (STP).
Experiments show that at STP, 1 mole of an ideal gas occupies 22.4 L

22. Examples
Sulfur dioxide is a gas produced by bruning coal. It is an air pollutant and one of the causes of acid rain. Determine the volume, in liters, of 0.60 mol of sulfur dioxide gas at STP.

23. *bonus
The density of a gaseous compound containing carbon and oxygen is found to be g/L at STP. What is the molar mass of the compound?

24. A block of dry ice (solid carbon dioxide) can be purchased in 4
A block of dry ice (solid carbon dioxide) can be purchased in 4.54 kg (10 lbs) blocks. How many liters of carbon dioxide gas will be released into the atmosphere when it sublimates ?