1. Notes: Limiting & Excess
WCHS Chemistry

2. NaHCO3 (s) + HC2H3O2 (aq) → H2CO3 (aq) + NaC2H3O2 (aq)
H2O (l) + CO2 (g)

3. LIMITING & EXCESS STOICH RULES
Rule #1: The limiting reactant controls your stoichiometry.
Limiting reactant = the one that you run out of first
Excess reactant = the one that is left over
Limiting
Frame + Wheels → Bike! 1 2 1 10 10 5
0.42 moles
0.84 moles
0.42 moles

4. LIMITING & EXCESS STOICH RULES
Frame + Wheels → Bike! 1 2 1 10 16 8
0.42 moles
0.62 moles
0.31 moles
Be careful!
Just because it’s the smallest number
Doesn’t mean it’s always limiting!

5. LIMITING & EXCESS STOICH RULES
Rule #2: CHECK THE RATIO !
Just because there is MORE of something doesn’t mean it is EXCESS!
Limiting & excess isn’t about which has more or less --- It’s about the ratio!

6. If you have 0. 30 moles of Ag(NO3)2 and 0
If you have 0.30 moles of Ag(NO3)2 and 0.50 moles of KCl, which is the limiting reactant? Which is excess?
Limiting!
Ag(NO3)2 + KCl → AgCl2 + KNO3 2 2
0.30 moles
0.50 moles
1:2 ratio
Need 0.60 KCl, but have less
Steps:
Balance: the coefficients tell you the ratio of moles!
Convert ALL given info into MOLES
Check your ratio, then label limiting reactant = the one that does not satisfy the RATIO