Pre-University Chemistry

1. Moles, Equations, and
Stoichiometry

2. Moles  Atoms
• How many sucrose molecules do you have if
the beaker contains 3.5 moles?
Hint:
How many bagels
do you have in
3.5 dozen?

3. 2.107 x 1024
1.How many molecules in 0.36 mol of water?
2.How many atoms are in 1.14 mol SO3?

4. Atoms  Moles
• If you have 5.75 x 1024
atoms of Copper, how
many moles do you have?

5. 9.55 moles
1.How many moles is 2.8 x 1024
atoms of silicon?
2.How many moles is 3.7 x 1024
molecules of CO2?

6. Balanced Equation
N2 + H2 → NH3
N2 + 3H2 → 2 NH3

7. Balanced Equation
N2 + 3H2 → 2 NH3
• Number of atoms
• Number of molecules
• Number of moles

8. Mole ratio
• N2 + 3H2 → 2NH3
• conversion factor derived from the
coefficients of a balanced equation

9. • N2 + 3H2 → 2NH3
• If you have 7 moles of H2 and you want to know
how much NH3
–What would you do?

11. Chemical Reactions???
Lets Start Over!
• What is a Chemical Reaction?
• What is all this math really about?

12. Chemical Reaction
• Combustion

13. Magnesium Oxide
1 Mg + 1 O  1 MgO
Mg + O  MgO
12Mg + 12O  12MgO
mol Mg + mol O  mol MgO

14. Chemical Reaction
• Combustion
2mol C2H2 + 5 mol O2  4 mol CO2 + 2 mol H20

15. Avogadro’s Number
6.02 × 1023
• Number of atoms in 12 grams of Carbon-12
Molar Mass
The mass of 1 mole of a substance

16. Molar Mass
Using the Periodic Table
N2 + 3H2 → 2 NH3
• mass of 1 mol of N2 =
28 g
• mass of 3 mol of H2 =
6 g
• mass of 2 mol of NH3 =
34 g

17. • If you find the mass of a sample of glucose
(C6H12O6) to be 90.0 g, how many moles of
glucose do you have?
• A certain laboratory procedure requires the
use of 0.100 moles of magnesium. How many
grams of magnesium would you mass out on
the balance?

18. 2 step problem
• What would be the mass of 3.75 x
1021
atoms of iron?
• First change number of atoms to moles
• Now, change number of moles to mass