1. Chapter 9
Chemical Reactions

2. INTRODUCTION TO CHEMICAL EQUATIONS
A chemical reaction (or chemical change) involves the formation of a __________________________.
reactants (starting materials) form a chemically different product.

3. INTRODUCTION TO CHEMICAL EQUATIONS
A chemical reaction equation uses

4. INTRODUCTION TO CHEMICAL EQUATIONS
Ex: 2H2 + O2 → 2H2 O
The word equation is: “Hydrogen gas reacts with oxygen gas to form water”.
Coefficient is ______________________________________________ ____________________________________ 

5. mass (reactants) = mass (products)
THE CONSERVATION LAWS
In a CLOSED system, the total mass of products is EQUAL to the total mass of reactants involved in a chemical reaction.
mass (reactants) = mass (products)
CLOSED when nothing can enter or leave the system.

6. THE CONSERVATION LAWS
Law of Conservation of Mass: states that the total ___________ of ALL REACTANTS before a chemical reaction equals the total __________ of ALL PRODUCTS after the chemical reaction.
For this to be true:
the total number of ___________ must be constant
bonds between atoms are broken and new bonds form...but same atoms are there

7. Examples

8. COUNTING ATOMS
Count the number of atoms in these compounds

9. COUNTING ATOMS
Count the number of atoms in these compounds

11. BALANCING CHEMICAL EQUATIONS
A balanced chemical equation is one in which the _____, the number of __________ on each side of the equation
( reactants side, products side) ARE CONSERVED AND EQUAL!
For our purposes, we will make sure that the number of a specific type of atom on the reactants side is always equal to the number of that same specific atom on the products side!

12. BALANCING EXAMPLE
Li O  Li2O

13. BALANCING CHEMICAL EQUATIONS
balance each side so the two sides are EQUAL
Equal means the number of atoms on each side of the equation is exactly the same
Balance by placing a ________________ in front of a formula ( coefficient)
NEVER everrrrrrrr change the ________________ on atoms (the little numbers on the bottom of formulas can’t be messed with )

14. BALANCING CHEMICAL EQUATIONS
Steps to balancing an equation (guidelines)
Start with atoms which occur once on each side
Balance the metals first (or any other non- hydrogen, non-oxygen atoms)
Balance polyatomic ions as a whole
Leave H and O until very last
*if a fraction (ex: 3/2) occurs during balancing, multiply the equation by the whole number denominator (ex:2) to eliminate the fraction.

16. BALANCING CHEMICAL EQUATIONS
___ Ca ___ H2O → ___ Ca(OH) ___ H2

17. BALANCING CHEMICAL EQUATIONS

18. VI.3 BALANCING CHEMICAL EQUATIONS

19. BALANCING CHEMICAL EQUATIONS

20. Balance (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O

21. HOMEWORK
Page 234
1,2,6,8,9

22. WRITING PHASES IN REACTION EQUATIONS & USING CHEMICAL WORD EQUATIONS
Phases are also shown in chemical reaction equations
s = solid phase
l = liquid phase
g = gaseous phase
aq = aqueous phase (dissolved in water)
ex: 2H2(g) + O2(g) → 2H2 O(g)
The word SOLID can also be stated as crystal, powder, and precipitate (precipitate is formed when two liquid or aqueous solutions react)

23. WRITING PHASES IN REACTION EQUATIONS & USING CHEMICAL WORD EQUATIONS
Diatomic molecules - seven of the elements form diatomic molecules:
N, O, F, Cl, Br, I and H
* on the periodic table, they form the shape of a 7 plus one (H)

24. Writing chemical equations from the word equation:
Ex #1: Liquid water reacts with powdered sodium oxide to form aqueous sodium hydroxide.

25. Examples
Ex #2: Solid aluminum oxide and aqueous sulphuric acid produce water and aqueous aluminum sulphate.

26. HOMEWORK