1. West Valley High School
Chapter 3B Notes Molar Relationships (the most important skill you will learn in chemistry!!!)
West Valley High School
General Chemistry
Mr. Mata

2. Molar Relationships
1 mole = 6.02 x 1023 atoms, molecules, or particles
Molar mass = mass of 1 mole of substance(Hint: Add up atomic masses)
Ex: Find the molar mass of:
H2O = (H=1(2), 0=16), 18 grams
CO2 = (C=12, O=16(2)), 44 grams
H2SO4=(H=1(2),S=32,O=16(4)), 98 g

3. Molar Masses Find molar masses: NaCl = CaCl2 = Fe(OH)2 = H3PO4 =
C6H12O6 =
Answers: 58 grams = 1 mol 110 grams = 1 mol 90 grams = 1 mol 98 grams = 1 mol 180 grams = 1 mol

4. Calculations: Converting moles to grams
Given # of mole X ? g (look at periodic table)= g
1 mole
How many grams of lithium are in 3.50 moles of lithium?
3.50 mole Li X 7 g = g Li
1 mol

5. Your turn… How many grams of carbon are in 8.25 moles of carbon?
8.25 mole C X 12 g = g C
1 mol

6. Your turn… How many grams of uranium are in 21.5 moles of uranium?
21.5 mole U X 238 g = g U
1 mol

7. Calculations: Converting grams to moles
Given # of g X 1 mol = mol
g (look at periodic table)
How many moles of lithium are in 18.2 grams of lithium?
18.2 g Li X 1 mol Li = 2.6 mol Li
7 g

8. Your turn… How many moles of gold are in 150 grams of gold?
150 g Au X 1 mol Au = 0.8 mol Au
197 g

9. Your turn… How many moles of H2O are in 120 grams of water?
120 g H2O X 1 mol H2O = 6.7 mol H2O
18 g

10. I didn’t discover it. Its just named after me!
Avogadro’s Number
Number of particles in exactly one mole of a pure substance.
6.02 x 1023 is called “Avogadro’s Number”.
Named in honor of the Italian chemist Amadeo Avogadro ( ).
I didn’t discover it. Its just named after me!

11. Chapter 3 HW (Back)
To find electrons, protons, and neutrons for an element:
40 Ca  atomic mass (#P + #N)
 atomic number (#P = #e)
# electrons = 20 (atomic number)
# protons = 20 (atomic number)
# neutrons = 20 (atomic mass–atomic #)
40 – 20 = 20 neutrons

12. Chapter 3 SUTW Prompt
Describe the contributions of Thomson, Millikan, & Rutherford to our understanding of the atom.
Complete a sentence paragraph using the SUTW paragraph format. Hilite using green, yellow, and pink.
Due Date: Tomorrow (start of class).