1. Physical and Chemical Changes
Physical Change: no composition change
Examples?
Chemical Change: composition changes
Chemical Reactions involve chemical changes
Chemical Equations describe chemical changes
(s)
solid
(l )
liquid
(g)
gas
(aq)
aqueous

2. Types of Reactions Combination Reactions + 2 + 2Mg O Mg O 2 + 2
Decomposition Reactions A B A B + O H O 2 2 H +

3. Types of Reactions Displacement Reactions Single Displacement + +B C C B A + A +
Double Displacement B B C C A + A + D D

4. Chemical Equations
Express identities and quantities of substances involved in chemical or physical change
Write reactants and products
Balance atoms (add coefficients)
Adjust coefficients (small-whole numbers)
Check balancing
Specify state of matter

5. The Mole 12 eggs = 12 bagels = 6.02 x 1023 hydrogen atoms =
6.02 x 1023 water molecules =
1 dozen eggs
1 dozen bagels
1 mol H atoms
1 mol H2O
1 mole is a unit that contains 6.02 x 1023
(Avogadro’s Number)
How many water molecules are in 3.5 moles of water?

6. Moles of Elements in a Formula
How many moles of each element are in 1 mole of water?
1 mole H2O = 1 mole O atoms
= 2 moles H atoms
How many moles of each element are in 1 mole of glucose?
1 mole C6H12O6 = 6 moles C atoms
= 12 moles H atoms
= 6 moles O atoms

7. Molar Mass
Number of grams of 1 mole of a substance is called its molar mass.
Same number as atomic or molecular mass
Examples:
Carbon
Water
Atomic mass:
12 amu
Molecular mass:
18 amu
Molar mass:
12 g
18 g
Molar mass:
Why do we use the unit of moles in lab instead of molecules or atoms?

8. Calculations with Molar Mass
You measure out 10.0 g of water. How many moles of water do you have?
If a piece of metal displaces 2.2 mL water,
how many water molecules has it displaced?
(Assume the density of water is 1.0 g/mL.)

9. Molar relationships
C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (g) 1 mol C3H8 reacts with _______ mols O2 1 mol C3H8 produces _______ mols CO2 1 mol C3H8 produces _______ mols H2O 5 mol O2 produces _______ mols CO2 2 mol C3H8 produces _______ mols CO2

10. Mass Calculations for Reactions
Write balanced equation
Convert given mass to mols
Convert to mols of other substance using stoichiometric equivalents
Convert amount of second substance to mass, number of entities, etc.

11. Sample Problem
How much carbon dioxide (in grams) is produced when 3.00 g of ethanol (C2H6O) combusts in air?
How much oxygen is used up to combust 5.00 g of ethanol?
C2H6O (l) + O2 (g)  CO2 (g) + H2O (l)

12. Limiting Reactants

13. Chemical Reactions Involving a Limiting Reactant
hydrazine (N2H4) and dinitrogen tetraoxide are liquids that ignite to form nitrogen gas and water vapor How many grams of nitrogen gas form when 100. g of N2H4 and 200. g of dinitrogen tetraoxide are mixed?

14. Chemical Reactions in Practice: Theoretical, Actual, and Percent Yields
Theoretical yield: what we should get
(according to calculations)
Actual yield: what we actually get
Why? Side reactions, error, etc.
Percent yield:

15. Oxidation-Reduction Reactions
Movement of electrons from one reactant to another
2 Mg (s) + O2 (g) --> 2 MgO (s)
Charge on magnesium? Oxygen?
LEO GER
Reducing agent? Oxidizing agent?

16. The reaction taking place in your engine is:
Your car has a 15 gallon gas tank. How many pounds of carbon dioxide are released to the atmosphere for ever tank of gas you use while driving your car?
The reaction taking place in your engine is:
Gasoline + Oxygen Carbon Dioxide + water
Hint: Gasoline is mostly Octane (C8H18)