1. Avogadro’s Law

2. What is Avogadro’s Law
Avogadro’s Principle – equal volumes of gases at the same temperature and pressure contain equal numbers of particles

3. This is a direct relationship!
Avogadro’s Formula
* n represents the amount of gas
V1= V2
n n2
This is a direct relationship!
So if the amount of gas increases, then the volume will ___________. If the amount of gas decreases, then the volume will __________.
increase
decrease

4. Graph for Avogadro’s Law
What Laws have we learned were also direct relationships, in which their graphs were similar to Avogadro’s?

6. **Conversion Factor: 1 mol (any gas) = 22.4 L at STP **
Avogadro’s Law
Molar Volume – for a gas is the volume that one mole of that gas occupies at STP
Avogadro showed experimentally that 1 mole of any gas will occupy a volume of 22.4L at STP
**Conversion Factor: 1 mol (any gas) = 22.4 L at STP **

7. Avogadro’s Law: Example 1
Calculate the volume that moles of oxygen gas at STP will occupy.

8. Avogadro’s Law: Example 1 Answer
Formula: V1 = V2 n1 n2
Remember, at STP:
22.4 L/mol
V1 = ? L
n1 = mol O2
V2 = 22.4 L
n2 = 1 mol O2
V = L
.881 mol O mol O2
After cross multiplying you end up with
V1(1 mol O2) = (22.4 L)(.881 mol O2)
1 mol O mol O2
V1 = ___________
19.7 L

9. Avogadro’s Law: Example 2
How many grams of N2 will be contained in a 2.0 L flask at STP? (Remember- one mole WEIGHS the formula mass in grams)

10. Avogadro’s Law: Example 2 Answer
Remember, at STP:
22.4 L/mol
V1 = 2.0 L
n1 = ? g N2
V2 = 22.4 L
n2 = 1 mol N2
Formula: V1 = V n1 n2
First , solve for the number of moles of N2:
2 L N2 | 1 mol N = mol N2
| 22.4 L N2
Then, use dimensional analysis to convert from moles of N2 to grams of N2:
.089 mol N2 | g N =
| mol N2\
2.5 g N2