1. Kiss My Molar Mass
Chapter 4, Section 2

2. Concept Review
Matter can be measured by counting (moles) or by weighing something (mass).
The Mole: Is the basic measuring unit of atoms/molecules.
It’s like a counting unit (like a dozen eggs!)
Avagodro’s Number= x 10 ^23

3. The mole
Is also associated with a mass. The mass of 1 mole of an element is equal to the atomic mass of the element in grams.
1 mole of Copper (Cu) = x 10^23 Cu atoms = g
(Atomic Mass#)

4. The size of a mole is equal to...
-A mole of grains of rice would cover all the land in the world to a depth of 75 meters!
-a mole of hockey pucks is roughly equal to the mass of the moon!
-A mole of baseballs would just about fit perfectly into a ball bag the size of the Earth!

5. How many moles?
For elements: 1 mole of element = x 10^23 atoms of element = X g, where X = Atomic Mass.
For compounds; 1 mole of compound = X 10^23 molecules of compound= Y g, where Y Molar Mass
Element/Comound
Formula
Fomula Mass (no Units)
Molar Mass (grams/mole)
Atomic Hydrogen H
1.01
1.01 g/mol
Molecular Hydrogen H2
2.02
2.02 g/mol
Carbon Dioxide
CO2
1(12.01) +2(16.00)
44.01 g/mol
Water
H2O
2(1.01)+1 (16.00)
18.02 g.mol

6. Finding the molar mass...
Page 127 #8: Determine the molar mass of each of the following elements:
Manganese, Mn c. arsenic, As
Cadmium, Cd d. Strontium, Sr
Molar Mass = The mass in grams of one mole of a substance
*1 mole of carbon-12 atoms has a mass of g, so the molar mass of carbon-12 is g/mol

7. Using Molar Mass: grams-to moles
Converting moles of a substance to mass in grams: moles x molar mass
Example: How many moles are in 23 grams of gold?
Step 1: Go to the periodic table and find the atomic mass of gold?
Atomic Mass of Au= g/mol
Step 2: Convert from grams to moles: (23 g Au) (1 mole/ g) = mol Au
Notice that the units of grams cancel!

8. Practice: Using Molar Mass: grams-to moles
Page 127 #15 and #16
-How many moles does 11 g of silicon, Si, contain?
Step 1: Go to the periodic table and find the atomic mass. AM of Si= g/mol
Converting moles of a substance to mass in grams: moles x molar mass
Step 2: Convert from grams to moles: (11 g of Si) (1 mole/28.09g/mol)
= mol *grams cancel out!

9. Practice: Using Molar Mass: grams-to moles
#16
How many moles does 205 g of helium, He, contain?
Step 1: Go to the periodic table and find the atomic mass.
Step 2: Convert from grams to moles:
Converting moles of a substance to mass in grams: moles x molar mass

10. Using Molar Mass: moles-to grams
Moles x (molar mass of element)/ 1 mol of element
Example: What is the mass of 54.5 mol of water?
Step 1: Go to the periodic table and calculate the molar mass of water: MM H2O = 2(1.01)+1(16.00)= g/mol
Step 2: Convert from moles to grams:
(54.5 mol H2O)(18.02 g/1 mol)=982 g water
Moles cancel out!

11. Practice:Using Molar Mass: moles-to grams
Page 127 #13 What is the mass in grams of 0.48 mol of platinum, Pt?
Step 1: Go to the periodic table and calculate the molar mass: MM = g/mol
Step 2: Convert from moles to grams:
Moles x (molar mass of element)/ 1 mol of element
(0.48 mol Pt)( g/mol) = *moles cancel out!

12. Practice:Using Molar Mass: moles-to grams
Page 127 #14: What is the mass in grams of 3.1 mol of mercury, Hg?
Step 1: Go to the periodic table and calculate the molar mass:
Step 2: Convert from moles to grams:
Moles x (molar mass of element)/ 1 mol of element

13. Your Turn
Using Molar Mass: grams-to moles
Problems 1,3,5,7
Using Molar Mass: moles-to grams
Problems 2,4,6,8