Name _____________________________ Hour ____
Stoich Notes (Part II)
Percent Yield
Theoretical Yield:

It comes from: ____________________
Experimental Yield:

It comes from: _____________________
Percent Yield Equation

Over 100% means: __________________________________________________________

Under 100% means: _________________________________________________________
Examples

When 84.8g of iron (III) oxide reacts with an excess of carbon monoxide, iron is produced. What is the
theoretical yield of iron in this reaction? Fe2O3(s) + 3CO(g)  2Fe(s) + 3CO2(g)

In an experiment, 50.0g of silicon dioxide is heated with an excess of carbon, 27.9g of silicon carbide is
produced. What is the percent yield of this reaction?
SiO2(s) + 3C(s)  SiC(s) + 2CO(g)
Limiting Reagent

Limiting Reagent/Reactant (LR):

Excess Reagent/Reactant (XS):
Making a grilled cheese sandwich: 2 pieces of bread + 1 piece of cheese = 1 sandwich
2B + C  B2C
Pieces of Bread
Pieces of
cheese
2
1
4
2
6
6
10
3
18
7
4
8
10
4
10
6
2
3
6
4
20
8
30
12
LR
XS
How many
sandwiches
made?
How much of
the XS reagent
left over?
Limiting Reagent Problems
Step by step
If 2.70 mol C2H4 is reacted with 6.30 mol O2, identify the limiting reagent.
C2H4(g) + 3O2(g)  2CO2(g) + 2H2O(g)
_______________________________________________________________________________
Step by step with grams
Identify the limiting reagent when 6.00g HCl reacts with 5.00g Mg.
Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)
_______________________________________________________________________________
Ex.4 What is the maximum number of grams of Cu2S that can be formed when 80.0g Cu reacts with
25.0g S?
2Cu(s) + S(s)  Cu2S(s)
_______________________________________________________________________________
Ex.5 If 2.70 mol C2H4 is reacted with 6.30 mol O2, identify the limiting reagent.
C2H4(g) + 2O2(g)  2CO(g) + 2H2O(g)