1. Topic: Names, Formulas, Equations, & Reactions
Aim: What conservation laws are important in chemical reactions, & how do we count atoms in a compound?
Do now:
Write the formula for chromium III oxide
HW:

2. Conservation of ENERGY
During any phys or chem change, the total quantity of energy remains constant.
Cannot be created or destroyed
Transferred to different forms
Ex. Lighting a match – chemical energy  light energy  thermal energy  chemical energy

3. Conservation of MASS
Products of a chemical reaction have the same mass as the reactants
Why equations must be balanced
That’s MY idea!
Antoine Laurent Lavoisier ( )

4. Conservation of CHARGE
The # of + or – charges on 1 side of the equation must equal the # of + or – charges on the other side
All compounds must be electrically neutral, + balances –

5. Counting the # of Atoms in a Compound
Subscript
# to the right & below a symbol
Tells # of atoms of that element
If the subscript is written after a polyatomic ion in parentheses, the subscript applies to each element in the parentheses – multiply
CO2
1 carbon, 2 oxygen
Mg(OH)2
1 magnesium, 2 oxygen, 2 hydrogen

6. Counting the # of atoms in a Compound
Coefficient
Written in front of a formula
Tells how many units of the formula are present & applies to the entire formula
4CO
4 carbon, 4 oxygen
4H2O
8 hydrogen (4x2), 4 oxygen

7. Counting the # of atoms in a Compound
NO subscript or coefficient implies 1
CO  1 carbon, 1 oxygen
BOTH a subscript & coefficient means multiply them
3CaSO4  3 calcium, 3 sulfur, 12 oxygen
4Mg(C2H3O2)2
4 magnesium, 16 carbon (2x2x4), 24 hydrogen (2x3x4), 16 oxygen (2x2x4)

8. Examples 2Na MgCl2 H2SO4 2H2O 4CaCl2 Na: 2 Mg: 1 Cl: 2 H: 2 S: 1 O: 4

9. Examples 2K3PO4 3Ca(NO3)2 Fe2(SO4)3 (NH4)2SO4 3Mg(C2H3O2)2

10. Examples 4Al(OH)3 CuSO4  5H2O 3MgSO4  7H2O 5Na2CO3 3Pb(SO4)2
2Ag3PO4 9C8H18 3Al2(SO4)3 4Fe3(PO4)2 2Mn(C2H3O2)7