1. Reference tables and calculators mandatory right now
OB: Mole class #2 Calculating Molar Masses, and numbers of atoms in any mass of an element or compound
Reference tables and calculators mandatory right now

2. (how many moles of each part are in one mole of compound?)
What is molar mass? How do we calculate it? What does it mean?
What’s the name for this compound?
Al(MnO4) __________________________
How do we calculate what one mole of this weighs?
(how many moles of each part are in one mole of compound?)
Al(MnO4)3 Al Mn O

3. (how many moles of each part are in one mole of compound?)
What is molar mass? How do we calculate it? What does it mean?
What’s the name for this compound?
Al(MnO4) Aluminum Permanganate
How do we calculate what one mole of this weighs?
(how many moles of each part are in one mole of compound?)
Al(MnO4)3
Al 1 x 27 g = g
Mn 3 x 55 g = g
O 12 x 16 g = g
384 g/mole

4. NYS Regents likes vocabulary. They like to use extra words like…
Gram Molecular Mass - another way to say molar mass for a molecular compound which forms into molecules Or
Gram Formula Mass - another way to say molar mass for an ionic compound that
makes formula units
Both of these mean molar mass, the number of grams in 1 mole of a substance. It’s just vocabulary, so don’t be fooled.

5. What is the gram molecular mass (the molar mass) of SULFUR TRIOXIDE?

6. SO3 S 1 mole x 32 g = 32 g O 3 moles x 16 g = 48 g 80 g/mole
What is the gram molecular mass (the molar mass) of sulfur trioxide?
SO3
S 1 mole x 32 g = g
O 3 moles x 16 g = 48 g
80 g/mole
The molar mass of sulfur trioxide is 80 grams
Or, if you have 80 grams of SO3, you have 1 mole of SO3
Or, 80 grams of SO3 = 6.02 x 1023 molecules of SO3

7. Calculate the gram formula mass (molar mass) of sodium sulfate
Calculate the gram formula mass (molar mass) of sodium sulfate. (write formula correctly first)
__________________________

8. Na2SO4 142 g/mole sodium sulfate. Na 2 moles x 23 g = 46 g
S 1 mole x 32 g = 32 g
O 4 moles x 16 g = 64 g
142 g/mole

9. Using the concept of moles and molar mass, you can determine how many moles are present in a given mass of a substance.
For example
If you have g of Nickel, how many moles do you have?
103.2 g Ni 1
Start at the beginning (please use units)

10. If you have 103.2 g of Nickel, how many moles do you have?
Using the concept of moles and molar mass, you can determine how many moles are present in a given mass of a substance.
For example
If you have g of Nickel, how many moles do you have?
103.2 g Ni 1
1 mole Ni
59 g Ni x =
1.749 moles of Nickel
4 SF
Unlimited SF
Needs 4 SF too

11. 551 grams of gold is how many moles of gold?

12. 551 grams of gold is how many moles of gold?
551 g Au 1
1 mole Au
197 g Au
2.80 moles Au x =

13. 13

14. 37.33 grams of silicon is how many moles of silicon?

15. Unlimited SF in this equality All molar masses have unlimited SF
37.33 grams of silicon is how many moles of silicon?
37.33 g Si 1
1 mole Si
28 g Si =
1.333 moles Si
(4 SF) x
Unlimited SF in this equality All molar masses have unlimited SF

16. Remember 6.02 x 1023 particles = 1 mole of anything
How many moles of zinc are in 1.25 x 1023 atoms?

17. How many moles of zinc are in 1.25 x 1023 atoms?
1.25 x 1023 atoms Zn 1
1 mole Zn x 1023 atoms Zn x =
1.25
6.02
1023
0.208 moles zinc x =
(3 SF)
This expression = 1

18. How many moles of xenon gas are in 8.75 x 1024 atoms of Xe?

19. 8.75 6.02 1024 1023 1.45 x 101 moles Xe = 14.5 moles Xe moles Xe = x
How many moles of Xe gas are in 5.75 x 1024 atoms of Xe?
8.75 x 1024 atoms of Xe 1
1 mole Xe 6.02 x 1023 atoms of Xe x =
8.75
6.02 x
moles Xe =
1.45 x 101 moles Xe = 14.5 moles Xe

20. Last slide o’ the day
If you find 50.0 grams of pure silver, how many atoms of silver did you find?
A hint might be required, this is a 2-step problem, first convert grams → moles, then Convert moles → atoms

21. 50.0 g Ag 1
1 mole Ag 108 g Ag X
= moles Ag
0.463 mole Ag 1
6.02 x 1023 atoms Ag 1 mole Ag X =
0.463 x 6.02 x 1023 atoms Ag = x 1023 atoms of silver
3SF

22. ( ) = 301 108 (1023 atoms Ag) 50.0 g Ag 1 1 mole Ag 108 g Ag
Or, do it all in one bigger math computation this way:
50.0 g Ag 1
1 mole Ag 108 g Ag
6.02 x 1023 atoms Ag 1 mole Ag X X =
( )
(50.0 X 1 X 6.02) X (1023 atoms Ag)
1 X 108 X 1 =
(1023 atoms Ag)
2.79 x 1023 atoms of silver
(3SF)