1. Bell Ringer
What is a Mole?
What is the mass of a NaCl molecule?

2. Chapter 7.1b
Molar Mass

3. Common counting units:
shoes by the pair (pair = 2)
eggs by the dozen (dozen = 12)
paper by the ream (ream = 500 sheets).

4. Counting With Moles
Chemical reactions usually involve very large numbers of tiny particles
We use a counting unit called the mole to measure amounts of a substance.
Mole (mol) = amount of any substance that contains approximately 6.02 × 1023 particles.
This amount is known as Avogadro’s number.
Ex: 1 mole of iron = 6.02 × 1023 atoms of iron.

5. Molar Mass: mass of one mole of a substance
same as atomic mass, in grams.
Examples:
Carbon:
Atomic mass = 12.0 amu
Molar mass = 12.0 grams.
Sulfur:
Atomic mass = 32.1 amu
Molar mass = 32.1 grams.

6. Counting With Moles Molar Mass of a compound =
sum of atomic masses of all its atoms, expressed in grams.
Tells us the total grams in one mole of the compound
Example: Carbon dioxide (CO2)
1 carbon atom = 12.0 amu
2 oxygen atoms = (2 × 16.0 amu) = 32.0 amu
CO2 atomic mass = ( ) = 44.0 amu
CO2 molar mass = 44.0 grams
44.0g CO2 in 1 mol CO2

7. Mole-Mass Conversions
Knowing the molar mass of a substance lets you easily convert between moles and mass
“converting” means you can calculate one from the other
Example:
Molar mass of CO2 is 44.0 grams
1.0 mole of CO2 = 44.0 grams
Conversion factors  OR

8. Converting Example: Chocolate Cake Recipe
Recipe calls for 4 eggs per cake and you plan to make 3 cakes. Eggs can only be bought by the dozen (i.e. groups of 12). How may dozen eggs do you need to buy?
Conversion factors: 4 eggs 1 cake cake 4 eggs
12 eggs 1 doz. eggs doz. eggs 12 eggs
Calc: 3 cakes x 4 eggs x 1 doz eggs = 1 doz eggs
1 cake eggs

9. Counting With Moles You have 55.0 grams of CO2. How many moles?
To calculate how many moles of CO2 you have, multiply the mass by a conversion factor.
You can check your answer.

10. Chemical Calculations
In chemical reactions, the mass of a reactant or product can be calculated.
Use a balanced chemical equation and the molar masses of the reactants and products.

11. Chemical Calculations
In a balanced chemical equation, the number of atoms of each element on the left equals the number of atoms of each element on the right.

12. Chemical Calculations
The Coefficient tells us the # of moles of each reactant and product involved the reaction

13. Chemical Calculations
Molar Mass = the # of grams per mole of each reactant and product

14. Chemical Calculations
Mass (of a reactant or product) =
the # of moles in the balanced equation (Coefficient) x the molar mass.

15. Chemical Calculations - Stoichiometry
Converting Mass to Moles
To calculate how much oxygen is required to make 144 grams of water, begin with a balanced chemical equation for the reaction.
2H2 + O2  2H2O
Determine how many moles of water you are trying to make.
Convert the given mass (144g) of water into moles.

16. Chemical Calculations
Using Mole Ratios
Write the conversion factors, or mole ratios.
2H2 + O2  2H2O
Calculate how many moles of oxygen are required to produce eight moles of water.

17. Chemical Calculations
Converting Moles to Mass
Convert moles of O2 to grams of O2 by using the molar mass of O2 as a conversion factor.
To produce 144 grams of H2O, you must supply 128 grams of O2.

18. Assessment Questions
Which of the following is a balanced chemical equation for the reaction of aluminum and ammonium perchlorate?
Al + NH4ClO4 —› Al2O3 + NH4Cl
4Al + 3NH4ClO4 —› 4Al2O3 + 3NH4Cl
8Al + NH4ClO4 —› 4Al2O3 + NH4Cl
8Al + 3NH4ClO4 —› 4Al2O3 + 3NH4Cl

19. Assessment Questions
Which of the following is a balanced chemical equation for the reaction of aluminum and ammonium perchlorate?
Al + NH4ClO4 —› Al2O3 + NH4Cl
4Al + 3NH4ClO4 —› 4Al2O3 + 3NH4Cl
8Al + NH4ClO4 —› 4Al2O3 + NH4Cl
8Al + 3NH4ClO4 —› 4Al2O3 + 3NH4Cl
ANS: D

20. Assessment Questions
How many moles of NaCl (molar mass = 58.5) are there in a 5.85-gram sample?
58.5 mol
5.85 mol
0.10 mol
0.28 mol

21. Assessment Questions
How many moles of NaCl (molar mass = 58.5) are there in a 5.85-gram sample?
58.5 mol
5.85 mol
0.10 mol
0.28 mol
ANS: C

22. Assessment Questions
In the reaction shown below, how many grams of hydrogen are produced when 10 moles of potassium react with water? 2K + 2H2O —› 2KOH + H2
2.5 g
5 g
10 g
20 g

23. Assessment Questions
In the reaction shown below, how many grams of hydrogen are produced when 10 moles of potassium react with water? 2K + 2H2O —› 2KOH + H2
2.5 g
5 g
10 g
20 g
ANS: C

24. Assessment Questions
In the chemical equation below, the reactants are carbon dioxide and water. CH4 + 2O2 —› CO2 +2H2O True <or> False?
ANS: False, products