1. Chapter 17

2. Balancing Chemical Equations
Reactants Products
2H2(g) + O2(g) → 2H2O(l)
coefficents
yields/produces
reacts with
reactants Products (g) = gas
H=4 H=4 (l) = liquid
O=2 O=2 (s) = solid
(aq) = aqueous solution

3. 2H2(g) + O2(g) → 2H2O(l)
4 atoms
of H
2 atoms
of O
4 atoms of H
2 atoms of O
When balancing equations… ONLY THE COEFFICIENTS CAN CHANGE.. NEVER CHANGE THE SUBSCRIPT!!!

4. 17.2 Balancing equations
The law conservation of mass is applied by balancing the number and type of atoms on either side of the equation.

5. 17.2 Balancing equations
Counting atoms is necessary to balance an equation.
How many carbon atoms?
How many hydrogen atoms?
How many oxygen atoms?

6. 17.2 Steps for balancing
Count the number of each type of atom on both sides.

7. Balancing Equations Balance the metals
Balance the nonmetals ( except for hydrogen and oxygen)
Then balance the hydrogen and oxygen

8. Let’s begin balancing equations
Example 1 __Al + __HCl → __AlCl3 + __H2 Example 2 __C2H4 + __O2 → __CO2 + __ H2O Example 3 __C5H10 + __O2 →__CO2 + __H2O

9. Example 4 __Zn + __AgNO3 → __Ag + __Zn(NO3)2 Example 5 __NH3 + __O2 → __NO + __H2O Example 6 __AlBr3 + __K2SO4 → __KBr + __Al2(SO4)3

10. Basic Types of Reactions
I. Combustion Reactions
Involve hydrocarbons(Carbon & Hydrogen) and related compounds reacting with O2 to form CO2 and H2O.
Ex1.
2C3H O2 → 6CO H2O
Ex2.
2CH3OH + 3O2 → 2CO H2O

11. Addition/Combination Reactions
Involve two or more substances which react to form one product.
A + B → C
Ex1.
C(s) + O2(g) → CO2(g)
Ex 2.
CaO(s) + H2O(l) → Ca(OH)2(s)

12. Decomposition Reactions
Occurs when one substance undergoes a reaction to produce two or more substances.
C → A + B
Ex1.
2KClO3(s) → 2KCl(s) + 3O2(g)
Ex2.
2Na3N(s) → 6Na(s) + N2(g)

13. Single Replacement
A + BX = AX + B
Example:
Fe + CuCl2 → FeCl2 + Cu

14. Double Replacement AB + CD → AD + CB Example:
Pb(NO3)2 + 2KI → PbI2 + 2KNO3

15. Atomic & Molecular Weights
Chemical formulas and chemical equations have quantitative significance. H2O means 2 atoms of hydrogen and 1 atom of oxygen. C3H8 + 5O2 → 3CO2 + 4 H2O means 5 moles of oxygen gas

16. Ex 1 Find the molecular weight of sucrose(C12H22O11)
Ex 1 Find the molecular weight of sucrose(C12H22O11). Ex 2 Find the formula weight of Ca(NO3)2. Ex 3 Find the formula weight of Al(OH)3.

17. 6.02 x 1023 The Mole Amedo Avogadro (1776-1856) determined the Mole’s
The mole – A collection of Avogadro’s number of objects
6.02 x 1023
Amedo Avogadro ( ) determined the Mole’s
number by experimentation
1 mole of 12C-atoms = 6.02 x C-atoms
1 mole H2O molecules = 6.02 x 1023 H2O molecules
1 mole NO3- ions = 6.02 x 1023 NO3- ions