1. Chapter 9 Chemical Quantities in Reactions
9.1 Mole Relationships in Chemical Equations
Learning Goal Given a quantity in moles of a reactant or product, use the mole– mole factor from the balanced equation to calculate the number of moles of another substance in the reaction.
© 2014 Pearson Education, Inc.

2. Calculating a Percentage (1.4C) Core Chemistry Skills
Chapter 9 Readiness
Key Math Skills
Calculating a Percentage (1.4C)
Core Chemistry Skills
Counting Significant Figures (2.3)
Using Significant Figures in Calculations (2.4)
Writing Conversion Factors from
Equalities (2.6)
Using Conversion Factors (2.7)
© 2014 Pearson Education, Inc.

3. Chapter 9 Readiness
Core Chemistry Skills (continued)
Using Energy Units (3.4)
Calculating Molar Mass (7.2)
Using Molar Mass as a Conversion
Factor (7.3)
Balancing a Chemical Equation (8.2)
Balancing Combustion Reactions (8.3)

4. Law of Conservation of Mass
The law of conservation of mass indicates that in an ordinary chemical reaction
matter cannot be created or destroyed
no change in total mass occurs in a reaction
mass of products is equal to mass of reactants

5. Law of Conservation of Mass
Tarnish (Ag2S) forms when silver reacts with sulfur in the air to form silver sulfide. The law of conservation of mass states:
2Ag(s) S(s)  Ag2S(s)
2 mol Ag mol S = 1 mol Ag2S
2(107.9 g) + 1(32.07 g) = 1(247.9 g)
In the chemical reaction of Ag and S, the mass of the reactants is the same as the mass
of the product, Ag2S.

6. Information from a Balanced Equation

7. Mole−Mole Factors from a Balanced Equation
A mole−mole factor is a ratio of the moles for two substances in an equation.
2Fe(s) S(s)  Fe2S3(s)
Fe and S
Fe and Fe2S3
S and Fe2S3

8. Learning Check
Consider the following equation:
3H2(g) N2(g)  2NH3(g)
A. A mole factor for H2 and N2 is
B. A mole factor for NH3 and H2 is

9. Solution
Consider the following equation:
3H2(g) N2(g)  2NH3(g)
A. A mole factor for H2 and N2 is
B. A mole factor for NH3 and H2 is

10. Guide to Calculating Quantities of Reactants and Products

11. Calculating Moles of a Reactant
How many moles of Fe are needed for the reaction of 12.0 moles of O2?
4Fe(s) + 3O2(g)  2Fe2O3(s)
Step 1 State the given and needed quantities (moles).
Given: moles of O2
Need: moles of Fe

12. Calculating Moles of a Reactant
How many moles of Fe are needed for the reaction of 12.0 moles of O2?
4Fe(s) + 3O2(g)  2Fe2O3(s)
? mol mol
Step 2 Write a plan to convert the given to the needed quantity of moles.
moles of O moles of Fe
Mole−Mole factor

13. Calculating Moles of a Reactant
How many moles of Fe are needed for the reaction of 12.0 moles of O2?
4Fe(s) + 3O2(g)  2Fe2O3(s)
? mol mol
Step 3 Use coefficients to write
mole−mole factors.
3 moles of O2 = 4 moles of Fe

14. Calculating Moles of a Reactant
How many moles of Fe are needed for the reaction of 12.0 moles of O2?
4Fe(s) + 3O2(g)  2Fe2O3(s)
? mol mol
Step 4 Set up the problem to give the needed quantity (moles).
Three SF’s Exact Three SF’s

15. Learning Check
How many moles of NO2 can be produced when 3.0 moles of O2 react?
N2(g) + 2O2(g)  2NO2(g)

16. Solution
How many moles of NO2 can be produced when 3.0 moles of O2 react?
N2(g) + 2O2(g)  2NO2(g)
Step 1 State the given and needed quantities (moles).
Given: 3.0 moles of O2
Need: moles of NO2

17. How many moles of NO2 can be produced when 3.0 moles of O2 react?
Solution
How many moles of NO2 can be produced when 3.0 moles of O2 react?
N2(g) + 2O2(g)  2NO2(g)
3.0 mol ? Mol
Step 2 Write a plan to convert the given to the needed quantity of moles.
moles of O moles of NO2
Mole−Mole factor

18. Solution
How many moles of NO2 can be produced when 3.0 moles of O2 react?
N2(g) + 2O2(g)  2NO2(g)
3.0 mol ? Mol
Step 3 Use coefficients to write mole−mole factors.
2 moles of O2 = 2 moles of NO2

19. Solution
How many moles of NO2 can be produced when 3.0 moles of O2 react?
N2(g) + 2O2(g)  2NO2(g)
3.0 mol ? Mol
Step 4 Set up the problem to give the needed quantity (moles).
Two SF’s Exact Two SF’s