1. Units 3 and 4: States of Matter and Solutions
Phase changes and solutions only involve the breaking and forming of intermolecular forces
Physical Changes!!! – No new substances were ever formed

2. Units 5,6 and 7: Chemical Reactions
Chemical reactions involve the breaking and forming of intramolecular forces (covalent/ionic/metallic bonds)
Chemical Changes!!! – New substances are formed

3. The key to ANY stoich. problem is converting any species to moles!
Basic Stoichiometry:
Equation must be
balanced …
P4 (s) + Cl2 (g)  PCl3 (l)
1 P4
12 P4
The key to ANY stoich. problem is converting any species to moles!
1 dozen P4
1 moles P4
3 moles P4
12 moles PCl3

4. Basic Stoichiometry: P4 (s) + Cl2 (g)  PCl3 (l)
Assuming there is enough Cl2 gas to completely react with 1.45 g of phosphorus, how many grams of PCl3 should be produced?
On your own: How much of the Cl2 gas was needed to react completely with the 1.45 g of phosphorus?

5. Limiting Reagants: 2 Na + Cl2  2 NaCl
Everyone knows the sandwich analogy
2 Na + Cl2  2 NaCl
If equal masses of each reactant are mixed (750 g), which is the limiting reactant and how many grams of sodium chloride is produced?
How much of the excess reagant is left over?

6. Percent yield: Stoichiometry only gives you theoretical yields.
Al4C3 (s) + H2O (l)  Al(OH)3 (s) + CH4 (g)
If 125 grams of aluminum carbide is reacted with 200. grams of water. What is the limiting reagent and how much methane can be produced?
If 13.6 grams of methane is obtained, what is the % yield of this gas?

7. Try the following now:
#1, 2 and 3
For Homework:
#4, 5, & 6