1. Molar Mass and Dimensional Analysis
Target 5: I can determine the molar mass and % composition of a compound.
-count the number of atoms in a compound.
-calculate the molar mass of a binary compound.
-calculate the molar mass of a compound with subscripts
-calculate the % composition of a compound.
Target 6: I can use dimensional analysis to convert between mass, mols, and particles.
-choose the correct conversion factor.
-convert between mass and mols.
-convert between molecules and mols.
-convert between mass and molecules.

2. 6.02 X 1023 atoms(or molecules)= 1 mole
What is a Mole?
A mole is a specific quantity
6.02 X 1023 atoms(or molecules)= 1 mole
It is like say you have a dozen roses instead of 12 roses.
You would say “I have a mole of Oxygen”
instead of “I have 6.02 X 1023 molecules of Oxygen”
The quantity 6.02 X 1023 is named for Amedeo Avogadro and is called
AVOGADRO’S NUMBER

3. What is a Mole? 1 dozen cookies = 12 cookies
1 mole of cookies = 6.02 X cookies OR
1 dozen cars = 12 cars
1 mole of cars = 6.02 X cars
1 dozen Al atoms = 12 Al atoms
1 mole of Al atoms =6.02 X 1023 atoms
If we look at these quantities...
Even though we have the same number,
MASS is VERY different!

4. What is a Mole?
When we determine the mass of a mole, we have to look at the type of compound.
Each element has an average mass that is dependent upon the size of one atom.
When we have 6.02 X 1023 molecules of that atom, the mass, in grams, will be the average mass found on the periodic table.

5. The Mass of a Mole
Molar mass is the mass in grams of one mole of any pure substance.
The molar mass of any element is numerically equivalent to its atomic mass and has the units g/mol.
Ex. Iron(Fe)’s molar mass = g/mol,
Therefore, 1 mol Fe = g

6. Calculating Molar Mass
Molar mass is the mass in grams of 1 mol of a substance. -We calculate this by adding up the atomic masses Instructions: Step 1: Break the compound into elements. Step 2: Multiply each atomic mass by how many of that element there are. Step 3: Find the atomic mass for each element. Step 4: Add all of these together.

7. Step 1: Break the compound into elements.
element: pure chemical substance consisting of one type of atom. When we describe one element, we use the chemical symbol.
compound: a chemical combination of two or more different elements
- Each new capital letter represents a new element.
- Each subscript tells you how many of that element there is.
- If there is no subscript assume 1.
- Parentheses are distributive.

8. Practice Problems:Break the compounds down into their respective elements:
KBr
KMnO4
Na2S
Ca(CN)2
Ca(NO3)2
Fe2(SO4)3
Remember:
Each new capital letter represents a new element.
Each subscript tells you how many of that element there is.
If there is no subscript assume 1.
Parentheses are distributive.

9. Now that you can count elements in a compound, lets calculate a molar mass. Practice problem: 1)Calculate the mass of 1 mole of CaCl2 Step 1: Break the compound into elements. Step 2: Multiply each atomic mass by how many of that element there are. Step 3:Find the atomic mass for each element. Step 4: Add all of these together.

10. Percent Composition
The percent composition is the percentage, by mass, of each element in a compound.
The percent composition of any element in a compound can be found by dividing the mass of the element by the mass of the compound and multiplying by 100.

11. How do we calculate % comp?
Percent Composition (% comp.) is the mass percent for each element in a compound.
How do we calculate % comp?
Step 1: Find the Molar Mass of the compound.
Step 2: Pick an element. Divide the mass of this element in the compound by the Molar Mass of the compound.
**Don’t forget to account for the # of atoms of each element
Step 3: Multiply by 100 to get percentage.
Step 4: Repeat for each element in the compound.

12. Practice Problems:
1) Find the % comp of the elements in Na3PO4
2) Find the % comp of the elements in SnCl4

13. How do I use “moles”?
Avogadro’s #, which is the number of atoms in a mole, can be used to convert between molecules and moles. Use Avogadro’s # as a conversion factor X 1023 atoms = 1 mole The terms atoms, molecules, and particles can be used interchangeably.

14. Practice Problems: 1) How many mols of helium are there in 5
Practice Problems: 1) How many mols of helium are there in 5.6 x 1023 atoms of helium? 2) How many atoms of Iron are in 3 mols of Iron?

15. How do I use Molar Mass?
Molar mass can be used to determine how many mols of a substance you have OR It can determine how many grams of a substance are in a specific number of mols. We can use the equivalency 1 mol = X g as a conversion factor!

16. Using Molar Mass

17. Practice Problems:
1)Convert 835 grams of SO3 to moles.
2) How many molecules of CH4 are there in 18 moles?

19. Kinetic Molecular Theory
The kinetic theory is how particles move.
It states that particles in all forms of matter, (S, L, G), are in constant motion, (either “vibrating”, “sliding”, or “flying”.)

20. KMT Applied to Gases
Kinetic molecular theory states that gases are in motion. When we look specifically at their movements, there are a few assumptions that are made for gases.
Gases are composed of small particles.
These particles are in constant motion and collide with other particles. They will move in a straight path until force is applied.
When particles collide, kinetic energy, (K.E.), is conserved.
-K.E. is the energy in motion. These types of collisions are called “perfect elastic.”

21. Kinetic Molecular Theory
The kinetic theory is how particles move.
It states that particles in all forms of matter, (S, L, G), are in constant motion, (either “vibrating”, “sliding”, or “flying”.)

22. KMT Applied to Gases
Kinetic molecular theory states that gases are in motion. When we look specifically at their movements, there are a few assumptions that are made for gases.
Gases are composed of small particles.
These particles are in constant motion and collide with other particles. They will move in a straight path until force is applied.
When particles collide, kinetic energy, (K.E.), is conserved.
-K.E. is the energy in motion. These types of collisions are called “perfect elastic.”

23. What is Gas Pressure
-When a gas particle collides with an object, it exerts a small force.
-Gas pressure is the result of simultaneous collisions from billions of gas particles upon an object.

24. Gas Pressure Conversion Factors
The S.I. (metric) unit for pressure is the pascal, (Pa). This is to 1 N/m2
-The standard air pressure (at sea level) is about X105 Pascals.
-All of the following pressures are also equal to standard pressure:
1 atmosphere (atm) = 760 mm Hg = kPa =
1.013 bars=760 Torr= inches Hg =14.7 (psi)
Practice Problem: The pressure on top of Mt. Everest is 253 mm Hg. What is this pressure in units of atm?

25. How Altitude Affects Air Pressure
The higher up you go the less air molecules there are, so there are fewer collisions which will leads to less pressure.
Inverse Relationship: As altitude inc., pressure dec.
*Examples: This is the reason why your ears pop in elevators, planes, or driving up and down large hills.
Altitude
Air Pressure

26. P1V1 = P2V2 where P = pressure and V = volume
Boyle's Law
Boyle’s law states that the volume of a fixed amount of gas held at a constant temperature varies inversely with the pressure.
P1V1 = P2V2 where P = pressure and V = volume
Section 13-1

27. Practice Problem: 1. A 40.0 mL sample of gas has a pressure of 720 mmHg. The sample was compressed to 35.0 mL. What is the new pressure of the sample?

28. Charles's Law
As temperature increases, so does the volume of gas when the amount of gas and pressure do not change.
Kinetic-molecular theory explains this property.
Charles’s law states that the volume of a given amount of gas is directly proportional to its Kelvin temperature at constant pressure.
Section 13-1

29. Charles Law and Temperature
Typically we use temperature units such a degrees Celsius or degrees Fahrenheit. When we look at relationships between volume and temperature, we need an absolute scale for comparison.
Kelvin is the absolute scale degrees Celsius is based on.
Absolute zero is zero on the Kelvin scale. There is no temperature colder than absolute zero.
ᵒC = K