Chapter 4.2
Page 125 – 127

Mole
• The SI base unit that describes the amount of pure substance .
• Abbreviation = mol

How many is in a mole?
• 1 mol = 6.02 x 10 23 (Avogadro’s constant)

How many is 6.02 x 10 23 ?
• If you stack 6.02 x 10 23 sheets of paper, it will reach the sun!
• If you cover the United States with 6.02 x
10 23 popcorn kernels, it will cover the whole country 310 miles deep!

Molar Mass
• Mass in grams of 1 mole of a pure substance.
• The molar mass of an element is the same as the mass number in grams .

Example
• The mass number of magnesium is 24 amu, therefore the molar mass of magnesium is 24 grams.
• This means that one atom of magnesium weighs 24 amu and one mole of magnesium weighs 24 grams.

Practice: Find the molar mass
1.
Argon, Ar = _______
2.
Zinc, Zn = _______
3.
Barium, Ba = _______
4.
Silver, Ag = ________

Practice: Find the molar mass
1.
Argon, Ar = 40 g
2.
Zinc, Zn = 65 g
3.
Barium, Ba = 137 g
4.
Silver, Ag = 108 g

Converting moles to mass
• Multiply the number of moles by the molar mass moles x molar mass = mass in grams

Converting moles to mass
Determine the mass in grams of 5.50 mol of iron.
5.50 mol Fe x 56 g Fe = 308 g Fe
1 mol Fe

Answer to Practice Problems
1) 80 g, S
2) 72 g, Ca
3) 6 g, C
4) 205 g, Cu

Converting mass to moles
• Divide the mass by the molar mass mass / molar mass = number of moles

Converting mass to moles
Determine the amount of iron in 352 grams of iron.
352 g Fe x 1 mol Fe = 6.3 mol Fe
56 g Fe

Answer to Practice Problems
1) 5.1 mol C
2) .62 mol Hg
3) 1.4 mol Ti
4) 7.1 mol N