1. Limiting Reagent and Percent Yield

2. Always start with the balanced equation
N2(g) + 3H2(g) → 2NH3(g)
The mole ratio is 1:3:2
If we have 1 mole of N2 and 6 moles of H2 what is the limiting reagent?
What is the excess reagent?

3. Excess reagent – the reactant that is present in more that he required amount for a complete reaction
Limiting reagent – the reactant that is completely consumed in a chemical reaction

4. To solve these problems use the mole bridge
Remember:
Only moles can cross
Specifically only the original mole can cross
And to cross you need to multiply or divide

5. You need a 1:1 comparison to decide who crosses!
0.75 mol of Iron react with 0.6 mol of oxygen to form iron(III)oxide.
How many moles of iron(III)oxide form?
4Fe O → Fe2O3
0.75 mol
0.60 mol
X mol
You need a 1:1 comparison to decide who crosses!

6. 4Fe O → Fe2O3
0.80 mol
0.60 mol
X mol

7. 4Fe O → Fe2O3
0.85 mol
0.60 mol
X mol

8. Percentage Yield
Yield - the quantity of product produced in a chemical reaction
IE what you get from the reaction

9. Two kinds of yield:
Actual Yield: what is actually produced or what you can measure after the reaction
Theoretical yield: the amount you calculate based on the balanced equation

10. Theoretical Yield 4Fe + 3O2 → 2Fe2O3
M = g/mol g/mol g/mol
10.00 g
10.00 g
Theoretical
Yield?

11. Theoretical Yield 4Fe + 3O2 → 2Fe2O3
M = g/mol g/mol g/mol
10.00 g
10.00 g
Theoretical
Yield = g

12. Percentage Yield
The theoretical yield for a reaction is g and the actual
Yield is g. What is the %yield?

13. So what? Environment: Money Chemical waste Is connected to
Poor yielding reactions
Money