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I. Atomic Mass1. The unit of an element is an atomic mass unit
(amu).
2. Carbon –12 has an atomic mass unit of 12. The atomic masses of other elements are found by comparing them to carbon-12.
3. Average atomic mass – the average of the atomic masses of the naturally occurring isotopes of an element.
REVIEW: WHAT’S AN ISOTOPE?
4. These are the numbers found on the periodic table.
II. THE MOLE, AVOGADRO’S NUMBER, MOLAR MASS
1. A mole is the SI unit for the amount of substance.
2. A mole is like a dozen. a) How many “things” are in a dozen?
b) How many “things” are in a mole?
II. THE MOLE, AVOGADRO’S NUMBER, MOLAR MASS
3. This number is called Avogardro’s Number.
4. Why was this number chosen? With this number of atoms, the mass in grams can be found on the periodic table
EX: 1 mol H atoms = 1.0079grams
(6.022x1023 atoms = mass from PT for each element)
HOW MANY ATOMS IN EACH
COMPOUND?1. AgBr
2. C2H6
3. NaHCO3
4. Fe2O3
5. Ca(OH)2
6. Ca3(PO4)2
Molar Mass Calculations
Definition: the mass, in grams, of one mole of a substance.
Example #1
NaCl
Molar Mass #2
O2
Molar Mass #3
C13H18O2 (ibuprofen)
Molar Mass #4
Ca(NO3)2
Exit 2/25/13:
Calculate the molar mass:
1. K2SO4
2. Al(OH)3
III. CALCULATIONS WITH EXPONENTS
Note: When typing powers of 10 in your calculator, NEVER type x 10. Instead, x 10 = EE or EXP button.
For example, 2 x 102 you would type 2 EE/EXP 2.
EXAMPLES:
1. (3.452x1024) = (6.022x1023)
2. (6.022x1023) x (23.45) =
IV. CALCULATIONS
(FACTOR LABEL
PROBLEMS!)The arrows represent the necessary
_______________________.
STP:
IV. CALCULATIONS
(FACTOR LABEL
PROBLEMS!)For gases at STP only!
EXAMPLES: Mass-Mole:
WHAT COVERSION FACTOR WILL YOU
USE?
EXAMPLES: Mass-Mole:
1. What is the mass in grams of 3.5 mol of the element copper, Cu?
a. b. c.
Mass-Mole:
2. A chemist produces 11.9g of aluminum, Al. How many moles of aluminum were produced?
a. b. c.
Mass-Mole:
3. How many moles of calcium chloride (CaCl2) are in 5.00g?
a. b. c.
Mass-Mole:
4. What is the mass in grams of 2.25 mol of ammonium hydroxide (NH4OH)?
a. b. c.
Mass-Mole:
5. How many moles are in 102.02g of calcium carbonate (CaCO3)?
a. b. c.
Mole-Particle:
WHAT CONVERSION FACTOR WILL YOU
USE?
Mole-Particle:
6. How many moles of silver, Ag, are in 3.01x1023 atoms of silver?
a. b. c.
Mole-Particle:
7. How many atoms of aluminum chloride are in 2.75 mol?
a. b. c.
Mole-Particle:
8. How many molecules are in 4.21moles of CO2?
a. b. c.
Mole-Particle:
9. How many atoms of sodium are in 2.75 mol?
a. b. c.
Mole-Particle:
10.How many moles are in 5.02x1023 molecules of water?
a. b. c.
Exit 3/1/13
1. Calculate the number of grams in 0.63mol of hydrogen atoms (H2).
2. How many oxygen atoms (O2) are in 4.5mol?
Warm-up
1. Find the number of moles in 5.62g of F2.
2. How many atoms is this?
Mass-Mole-Particle:
11.What is the mass in grams of 1.20x108 atoms of copper?
a. b. c.
Mass-Mole-Particle:
12.How many atoms of sulfur are in 4.00g?
a. b. c.
Mass-Mole-Particle:
13.What is the mass in grams of 6.23x108 atoms of gold?
a. b. c.
Mass-Mole-Particle:
14.How many atoms are in 10.00g of silver?
a. b. c.
Mass-Mole-Particle:
15.What is the mass in grams of 3.45x1024 atoms of calcium?
a. b. c.
Mass-Mole-Particle:
16.How many atoms of tungsten are in 7.00g?
a. b. c.
Exit Slip
1. How many atoms of iron are in a 6.73g sample?
2. How many grams of He are in 2.0x1023 atoms?
Volume of a Gas:
17.Determine the volume, in liters, of 0.60mol SO2 gas at STP.
a. b. c.
Volume of a Gas:
18.What is the volume of 0.960mol of CH4 at STP?
a. b. c.
Volume of a Gas:
19.How many moles are in 67.2L of SO2 at STP?
a. b. c.
Volume of a Gas:
20.Determine the moles of 0.880L of He at STP.
a. b. c.
