1. Notes #2: Stoichiometry
WCHS Chemistry

2. REMINDERS! Moles = Mass FW Al + O2 → Al2O3 4 3 2
Coefficients DO NOT affect formula weight!
Subscripts DO affect formula weight
Coefficients tell you RATIO of MOLES (not grams)
If you know moles of one thing, you’re a RATIO away from knowing the moles of everything!

3. Al + O2 → Al2O3 4 3 2 x 2 STEPS: Life starts with a balanced equation!
Moles = Mass FW
? g
STEPS:
Life starts with a balanced equation!
30.6 g
If you’re given grams, convert grams → moles
30.6 g Al2O3
= 0.30 moles Al2O3
102 g/mol Al2O3
Use the mole ratio (coefficients) to get moles of what you want!
x 2
0.30 mol Al2O3
= 0.60 moles Al
Convert moles → grams using THAT formula weight
0.60 moles Al
x 27 g/mol Al
= 16.2 g Al