7.1: “Avogadro’s Number and Molar Conversions” Day 2
1. Molar mass: the mass in _________ of one ___________ of an element or compound.
a. Molar mass is numerically __________ to the __________ mass of
_____________ and the formula mass of _______________ (H 20, CH4, etc) and
diatomic elements. (O2, F2, etc.)
b. The units for molar mass are _______________.
2. Molar Mass Example #1: What is the molar mass of water, H2O?
3. Molar Mass Example #2: What is the molar mass of sulfuric acid, H2SO4?
4. Molar Mass Example #3: What is the molar mass of sodium carbonate, Na2CO3?
5. Molar mass can be used as a conversion factor to change from _______________ (in
grams) to ____________________ (in moles)!!
6. Changing Moles
Mass (in grams)
Determine the mass in grams of 3.50 mol of copper, Cu.
1.
Start with what you know: 3.50 mol Cu
2. Use the molar mass of Cu as the conversion factor to change mol Cu
3.50 mol Cu X 63.55 g Cu
=
222 g Cu (3 sig figs)
1 mole Cu
7. Changing Moles
Mass (in grams) Example #1
What is the mass in grams of 10.5 mol ammonia, NH3?
8. Changing Moles
Mass (in grams) Example #2
How many grams are in 1.26 moles of aluminum hydroxide, Al(OH)3?
grams Cu.
9. Changing Mass (in grams)
Moles
How many moles of helium are contained in 0.255 g of He?
1.
Start with what you know: 0.255 g He
2. Use the molar mass of He as the conversion factor to change mass He
0.255 g He X 1 mol He
=
.0638 mol He (3 sig figs)
4.00 g He
10. Changing Mass (in grams)
Moles, Example #1
How many moles are there in 68 g of copper (II) hydroxide, Cu(OH)2?
11. Changing Mass (in grams)
Moles, Example #2
How many moles are there in 1,200 g of ammonia, NH3?
mol He