1. Launch: 11/25
 Grab you binder and immediately take a seat!
 Place homework (practice questions) on desk
1. Calculate the molecular mass for the following:
1. F2
2. H2S
3. H3PO4
4. Al(OH)3

2. Launch 11/25
5. How many moles are there in 6g of carbon-12?
a. .5 moles
b. 1 mole
c. 2 moles
d. 12 moles

3. Announcements
 Today’s lesson is really important!
 Points end today!
 Block 1 is in the lead
 Be respectful

4. How many moles?
Mr. Heffner
11/25/09

5. Review: What is a molar mass?
 Molar mass is…
 the sum of the atomic masses in a molecule
H 2O
Molar mass = mass of H + mass of H + mass of O
= 1.01 + 1.01 + 16.00
= 18.02 g/mol Units!

6. How many moles?
 Molar mass is…
 a conversion factor
 used to convert between grams and moles
Molar mass of H2O = 18.02 g/mol
18.02 grams 1 mole“grams
or divided by
1 mole 18.02 grams
moles”

7. How many moles?
 There is a 3-step process:
1. Write down the starting unit.
2. Calculate molecular mass and turn it into a
conversion factor with the starting units on the
bottom.
3. Cancel units and multiply across the top and
bottom.

8. Example #1
How many grams of H2O are there in 2 moles of H2O?
 Step #1: Write down the starting unit.
2 moles

9. Example #1
How many grams of H2O are there in 2 moles of H2O?
 Step #2: Calculate molecular mass and turn it into a conversion
factor with the starting units on the bottom.
18.02 grams
2 moles X =
1 mole

10. Example #1
How many grams of H2O are there in 2 moles of H2O?
 Step #3: Cancel units and multiply across the top and bottom.
18.02 grams 2 X 18.02 grams
2 moles X =
1 mole 1
= 36.04 grams
units!

11. Example #2
How many moles of H2O are there in 9.01 grams of H2O?
 Step #1: Write down the starting unit.
9.01 grams

12. Example #2
How many moles of H2O are there in 9.01 grams of H2O?
 Step #2: Calculate molecular mass and turn it into a conversion
factor with the starting units on the bottom.
1 mole
9.01 grams X =
18.02 grams

13. Example #2
How many moles of H2O are there in 9.01 grams of H2O?
 Step #3: Cancel units and multiply across the top and bottom.
1 mole 9.01 X 1 mole
9.01 grams X =
18.02 grams 18.02
= .5 moles
units!

14. Example #3
How many grams of N2 are there in 3 moles of N2?
 Step #1: Write down the starting unit.
3 moles

15. Example #3
How many grams of N2 are there in 3 moles of N2?
 Step #2: Calculate molecular mass and turn it into a conversion
factor with the starting units on the bottom.
28.02 grams
3 moles X =
1 mole

16. Example #3
How many grams of N are there in 3 moles of N2?
 Step #3: Cancel units and multiply across the top and bottom.
28.02 grams 3 X 28.02 grams
3 moles X =
1 mole 1
= 84.06 grams
units!

17. Whiteboards
 Work in pairs
 Trade-off marker every question
 You have 60 seconds to draw the answer
 Show all of your work!
 Don’t forget units!
 Lift board only when prompted

18. What is the molecular mass
of O2?

19. Write the molecular mass of
O2 as a conversion factor.

20. How many grams of O2 are
there in 2 moles of O2 ?

21. How many grams of NaCl are
there in 3 moles of NaCl?

22. How many moles of O2 are
there in 320 grams of O2 ?

23. How many moles of Al(OH)3 are
there in 78.01 grams of Al(OH)3?

24. Practice Questions
 Practice question worksheet

25. Exit Slip
1. What is the molar mass of CH4?
a. 4.00 g/mol
b. 13.02 g/mol
c. 16.05 g/mol
d. 52.08 g/mol

26. Exit Slip
2. Which of the following is not a correct way to
represent the molecular mass of H2?
a. 2.02 g/mol
2.02 grams
b.
1 mole
c. 2.02 moles
1 gram
d. 1 mole
2.02 grams

27. Exit Slip
3. Which of the following shows the correct way to
calculate the number of moles in 12.01 grams of
carbon?
12.01 grams
a. 12.01 moles X 1 mole
1 mole
b. 12.01 grams X 12.01 grams
12.01 grams
c. 12.01 grams X
1 mole
12.01 grams
d. 1 mole X
1 mole

28. Exit Slip
4. How many grams of hydrogen (H) are there in 8
moles of H?
a. 1.00 grams
b. 1.01 grams
c. 5.05 grams
d. 8.08 grams

29. Exit Slip
5. How many moles of O2 are there in 16.00g of O2?
a. .5 moles
b. 1 mole
c. 2 moles
d. 16 moles

30. Homework
 Finish practice questions