1. Balancing and Chemical Reactions

2. Why do we have to Balance equations?
Hint: Think about Law of Conservation of Mass!
The # of atoms of each element must be equal on both sides of the equation.

3. Parts of a Chemical Equation
Parts of a Chemical Formula
Chemical formula is a math formula for science!
Label the different parts?
2Na + Cl2 2NaCl
Reactants=Left side of equation
Products=Right side of Equation
“yields, produces, forms”
Same as an = sign
“and”
Coefficient-used to balance a chemical equation
Subscript-determines how many atoms of an element are needed for the compound

4. Vocabulary Continued
3) Catalyst - substance that changes the rate of a chemical reaction but remains unchanged throughout the reaction

5. Symbols Yields: indicates result of reaction Reversible reaction
Indicates a precipitate (solid)
Indicates a gaseous product
(s) Reactant or product in a solid state
(l) Reactant or product in a liquid state
(g) Reactant or product in a gaseous state
(aq) Reactant or product in a aqueous state
Reactants are heated
Presence of a catalyst Pt

6. Steps to Balance an Equation
Step 1: List all the elements in the equation underneath the center of the equation
Step 2: Count how many of each element is on the reactant side then the product side
Step 3: Is this balanced or unbalanced
Step 4: balance the equation if necessary by adding coefficients

7. Practice _____ N2 + _____ H2 → _____NH3 N H
_____ KClO3 → _____ KCl + _____ O2 K Cl O

8. __ FeCl3 + __ NaOH → __ Fe(OH)3 + __ NaCl
___ Na + ___ H2O → ___ NaOH + ___ H2

9. __ C2H6 + __ O2  __ CO2 + __ H2O __ AlBr3 + __ K2SO4 → __ KBr + __ Al2(SO4)3

10. Types of Reactions Notes

11. Reduction-Oxidation Reactions (REDOX)
Reduction-Oxidation Reactions: any chemical reaction where elements undergo changes in oxidation number (charges)
How can I tell if this is REDOX or not?
Elements that are NOT in a compound will have a charge of ZERO.
Elements in compounds will have a CHARGE

12. REDOX Vocabulary
Reduced: the oxidation state (charge) of the element decreases from the reactants to the products
Oxidized: the oxidation state (charge) of the element increases from the reactants to products

13. Redox Reactions? Y OR N NaCl + F2  NaF + Cl2 P + O2  P2O5
FeCl3 + NaOH  Fe(OH)3 + NaCl
Ag2O  Ag + O2
S8 + O2  SO3

14. Precipitate Reactions
These are reactions where all of the pieces are rearranged from reactants to products and we get a precipitate (solid ) out.
Examples:
__ Al2(SO4)3 + __ K3PO4__ K2SO4 + __ AlPO4
__ FeCl3 + __ NaOH  __ Fe(OH)3+ __NaCl

15. Precipitate Vocabulary
Precipitate: solid produced within a solution as a result of a chemical reaction
Aqueous solution: a solution where the solvent is water

16. Acid/Base Reactions
This type of reaction involves an acid (a compound that starts with H) and a base (a compound that ends with an –OH) that make a salt and water.
Examples:
___Ca(OH)2 + ___HCl  ___CaCl2 + ___H2O
___H2SO4 + __NaOH  + __H2O + __Na2SO4

17. Energy in Reactions Endothermic vs. Exothermic Endothermic-
Energy moves from the surroundings into the source
EX: Cold packs, Alka seltzer
Exothermic-
Energy moves from the source out to the surroundings
EX: Light a match, fuel

18. Types of Reactions Notes

19. Why do chemicals react? You already know!!!!! Types:
To fill up their outer shells…
when we create chemical bonds we have a chemical reaction!!
Types:
Ionic
Covalent
Metallic

20. Types of Reactions: 5 types: Synthesis Decomposition
Single Displacement
Double Displacement
Combustion

21. Synthesis
Two or more elements combine to form 1 chemical compound
EX: 2Mg + O MgO
Analogy: One girl + One Boy = One couple
Generic equation:
A + B AB
Another example:
Water Formation

22. Decomposition
When a compound breaks into 2 elements or simpler compounds-“break down”
2NaCl = 2Na + Cl2
Analogy: One couple= One boy + one girl (Divorce)
Generic equation:
AB A + B
Another example: ”Electrolysis”
Decomposition

23. AB + C A + BC Single Displacement
A single uncombined element replaces another in a compound. Two reactants yield two products.
Analogy: A “playa girl” has a
boyfriend but likes a cuter boy instead
SD Animation
Generic Example:
AB + C A + BC
Example:
Lets visualize it!

24. Double Displacement
When one element of each compound changes places with the other element
Analogy: Two couples that switch partners
Generic Example:
AB + CD AC + BD
Example:
PbCl2 + Li2SO PbSO4 + 2LiCl DD RX

25. Combustion Reaction Combustion Reaction FIRE!!!!
What do we know as combustion?
FIRE!!!!
Requires a fuel and oxygen and produces CO2 and H2O
Releases so much energy a flame is released
Generic example:
Combustion Reaction
C(x)H(x)+O2→H2O(g)+CO2(g)

26. Balancing Chemical Equations
Why do we need to balance?
Law of Conservation of Mass-mass can not be created or destroyed, it is only changed to a different form
Everything on the left has to equal everything on the right!!!
Just like math… = 5 WRONG!!!
3 + 2 = 5 RIGHT!!!

27. Lets look at our equation..
2Na + Cl2 2NaCl
What did we call each part?

28. Word Equations Must know the Diatomic Molecules: Hydrogen – H2
Nitrogen – N2
Oxygen – O2
Fluorine – F2
Chlorine – Cl2
Bromine – Br2
Iodine – I2

29. Word Equations Practice
As I quoted “You cannot forget how to write formulas!”
Practice:
iron (III) chloride and ammonium hydroxide produce iron (III) hydroxide and ammonium chloride

30. Word Equations Practice
2) potassium and chlorine combine to form potassium chloride
3) ammonium nitrate yields dinitrogen monoxide and water

31. 4) dicarbon dihydride and oxygen produce carbon dioxide and water 5) aluminum bromide and chlorine react to form aluminum chloride and bromine