1. Notes 6-2
Chemical Reactions

2. Chemical Formulas
The formula of a compound identifies the elements in the compound and the ratios in which their atoms are present.

3. What Are Chemical Equations?
Chemical equations use chemical formulas and other symbols instead of words to summarize a reaction.

4. Law of Conservation of Matter
Matter is neither created nor destroyed
*It is simply rearranged!

5. Conservation of Matter
The law of conservation of matter states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products.

6. Balancing Chemical Equations
To describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.

7. Examples from your lab:
Acid + Base  Water + Salt
HCl + NaOH  H2O + NaCl
HCl + KOH  H2O + KCl

9. Let’s try some! 3 3 ____ AlBr3 + ____ K  ____ KBr + ____ Al
Count the atoms:
1 Aluminum atom Potassium atom 1 Potassium atom Aluminum atom
3 Bromine atoms Bromine atom
Is it balanced?
No!
Add coefficients to balance atoms:
1 Aluminum atom Potassium atoms 3 Potassium atoms Aluminum atom
3 Bromine atoms Bromine atoms
Is it balanced?
YES!

10. Let’s try some! ____ FeO + ____ PdF2  ____ FeF2 + ____ PdO
Count the atoms:
1 Iron Palladium Iron Palladium
1 Oxygen 2 Flourine 2 Flourine 1 Oxygen
Is it balanced?
YES!
Do we need to add coefficients?
NO!

11. Let’s try some! 6 4 ____ P4 + ____ Br2  ____ PBr3 Count the atoms:
4 Phosphorus Bromines Phosphorus
3 Bromines
Is it balanced?
No!
Add coefficients to balance atoms:
4 Phosphorus Bromines Phosphorus
12 Bromines
Is it balanced?
YES!

12. Let’s try a harder one! 2 3 3
____ CoBr3 + ____ CaSO4  ____ CaBr2 + ____ Co2(SO4)3
Count the atoms:
1 Co Ca Ca 2 Co
3 Br S Br 3 S
4 O O
Is it balanced?
No!
Add coefficients to balance atoms:
2 Co Ca Ca 2 Co
6 Br S Br 3 S
12 O O
Is it balanced?
YES!