Limiting Factors

1
Limiting Factors Percent Yield Quiz
Good Luck!!
2
Bell Ringer
When 6.58 g SO3 and 1.64 g H2O react, what is the
expected yield of sulfuric acid? If the actual
yield is 7.99 g sulfuric acid, what is the
percent yield?
SO3

H2O
H2SO4
1 mol SO3
1 mol H2SO4
98.09 g H2SO4
6.58 g SO3
x
x
x

80.07 g SO3
1 mol SO3
1 mol H2SO4
8.06 g H2SO4
1 mol H2O
1 mol H2SO4
98.09 g H2SO4
1.64 g H2O
x
x
x

18.02 g H2O
1 mol H2O
1 mol H2SO4
8.93 g H2SO4
3
Bell Ringer
When 6.58 g SO3 and 1.64 g H2O react, what is the
expected yield of sulfuric acid? If the actual
yield is 7.99 g sulfuric acid, what is the
percent yield?
SO3

H2O
H2SO4
Info weve learned
Theoretical Yield 8.06 g H2SO4
7.99 g H2SO4

99.1
8.06 g H2SO4
4
Stoichiometry Review

• Mr. Trotts

5
Things to know for test

• Stoichiometry the calculation of quantities in
  chemical reactions
• In every reaction mass and atoms are conserved
• Limiting reactant the reactant that is used up
  in a chemical reaction
• The amount of product obtained is determined by
  the limiting reagent
• The first step in any stoichiometry problem is to
  balance the equation by adding coefficients to
  the reagents
• In one mole of H20 there are 3 x 6.02x1023 atoms

6
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

7
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

8
Mole-Mole Problems

• 1 conversion step
• Given moles A
• Required moles B
• Convert moles A to moles B using mole ratio.
• The mole ratio is used in EVERY STOICHIOMETRY
  PROBLEM. EVER. I PROMISE.

How many moles of water can be formed from 0.5
mol H2?
2 mol H2O
0.5 mol H2
0.5 mol H2O
x

2 mol H2
9
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

10
Mass-Mole Problems

• 2 conversion steps
• Given mass A
• Required moles B
• Step 1 convert grams A to moles A using
  Periodic Table
• Step 2 convert moles A to moles B using mole
  ratio

How many moles of water can be formed from 48.0 g
O2?
2 mol H2O
1 mol O2
48.0 g O2
3.00 mol H2O
x

x
1 mol O2
32.00 g O2
11
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

12
Mass-Mass Problems

• 3 conversion steps
• Given mass A
• Required mass B
• Step 1 convert grams A to moles A using
  Periodic Table
• Step 2 convert moles A to moles B using mole
  ratio
• Step 3 convert moles B to grams B using
  Periodic Table

How many grams of water can be formed from 48.0 g
O2?
2 mol H2O
1 mol O2
18.02 g H2O
48.0 g O2
54.1 g H2O
x

x
x
1 mol O2
32.00 g O2
1 mol H2O
13
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

14
Mass-Volume Problems

• 3 4 conversion steps
• Given mass A
• Required volume B
• Step 1 convert grams A to moles A using
  Periodic Table
• Step 2 convert moles A to moles B using mole
  ratio
• Step 3 convert moles B to liters B

How many liters of oxygen are necessary to create
48.0 g H2O?
48.0 g H2O
1 mol O2
1 mol H2O
22.4 L O2
29.8 L O2
x

x
x
2 mol H2O
18.02 g H2O
1 mol O2
15
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

16
Volume-Mass Problems

• 3 4 conversion steps
• Given volume A
• Required mass B
• Step 1 convert liters A to moles A
• Step 2 convert moles A to moles B using mole
  ratio
• Step 3 convert moles B to grams B using
  Periodic Table

How many grams of water are formed by reacting
36.0 L O2?
36.0 L O2
2 mol H2O
1 mol O2
18.02 g H2O
58.7 g H2O

x
x
x
1 mol O2
22.4L O2
1 mol H2O
17
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

18
Volume-Volume Problems

• 3 5 conversion steps
• Given volume A
• Required volume B
• Step 1 convert liters A to moles A
• Step 2 convert moles A to moles B using mole
  ratio
• Step 3 convert moles B to liters B

How many liters of H2 are required to react with
5.0 L O2?
5.0 L O2
2 mol H2
1 mol O2
22.4 L H2
10. L H2
x

x
x
1 mol O2
22.4 L O2
1 mol H2
19
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

20
Limiting Reactant Problems

• Quantities are given for each reactant.
• 2 parallel equations
• Solve each equation for product desired and
  determine limiting reactant.
• Use Limiting Reactant to solve for amount or
  excess reactant used.
• Subtract amount excess reactant used from amount
  given to determine how much is left over.

21
Limiting Reactant Problems
If you start with 10.0 g of O2 and 5.00 g H2 how
much water would be formed? Which would be your
limiting factor? How much of the excess reagent
would there be?
1 mol O2
2 mol H2O
18.02 g H2O
10.0 g O2
x
x

x
32.00 g O2
1 mol O2
1 mol H2O
LIMITING REACTANT
11.3 g H2O
THEORETICAL YIELD
5.00 g H2
1 mol H2
2 mol H2O
18.02 g H2O
x
x

x
2.02 g H2
2 mol H2
1 mol H2O
EXCESS REACTANT
44.06 g H2O
22
Limiting Reactant Problems
2 H2

O2
2 H2O
If you start with 10.0 g of O2 and 5.00 g H2 how
much water would be formed? Which would be your
limiting factor? How much of the excess reagent
would there be?
Info we know so far Limiting Reactant
O2 Excess Reactant H2
2 mol H2
1 mol O2
2.02 g H2
10.0 g O2
x
x

x
1 mol O2
32.00 g O2
1 mol H2
1.26 g H2
USED
5.00 g H2 1.26 g H2
3.74 g H2
LEFT OVER
23
Types of Stoichiometry Problems

• Mole-Mole
• Mass-Mole
• Mass-Mass
• Mass-Volume
• Volume-Mass
• Volume-Volume
• Limiting Reactant
• Percent Yield

24
Percent Yield Problems

• Critical Information
• Theoretical Yield
• Actual Yield
• Percent Yield

Determine the actual yield of a reaction between
6.25 g H2 and excess O2 that has a 85 percent
yield.
6.25 g H2
1 mol H2
2 mol H2O
18.02 g H2O
x
x

x
2.02 g H2
2 mol H2
1 mol H2O
55.6 g H2O
THEORETICAL YIELD
?
85
100
x
55.6 g H2O
ACTUAL YIELD 47.3 g H2O
25

• Next class test
• Bring a calculator and extra paper to do your
  work on
• Packet due