1. Stoichiometry Introduction: Mole-Mole Relationships

2. Significance of Coefficients What do the coefficients in a chemical reaction represent? Ratio of molecules that react Ratio of moles that react

3. Take a look at this “recipe” for the formation of ammonia gas. N 2 (g) + 3 H 2 (g) → 2 NH 3 (g) We can combine 1 part N 2 and 3 parts H 2 to produce 2 parts NH 3. We would typically state that we can combine 1 mole N 2 and 3 moles H 2 to produce 2 moles NH 3.

4. This is the recipe for making sandwiches... What do you need to make a plain and ordinary ham sandwich? 2 Bread + 1 Ham → 1 Sandwich

5. Stoichiometry allows us to compare any two of the substances in a “recipe” at a time. Typical queries might be: How many sandwiches can I prepare with 12 pieces of bread? How much bread is needed to completely use 8 slices of ham when making sandwiches? If only 4 slices of ham are in my refrigerator, how many sandwiches can I make?

6. How many sandwiches can I prepare with 12 pieces of bread? 2 Bread + 1 Ham → 1 Sandwich x 12 Bread Bread Sandwich 2 1 6 Sandwiches =

7. How much bread is needed to completely use 8 slices of ham when making sandwiches? 2 Bread + 1 Ham → 1 Sandwich 8 Ham x Ham Bread 1 2 = 16 Bread

8. If only 4 slices of ham are in my refrigerator, how many sandwiches can I make? 2 Bread + 1 Ham → 1 Sandwich 4 Ham x Ham Sandwich = 1 1 4 Sandwiches “Mole Ratio” conversion step

9. Now, back to the reaction for the production of ammonia. N 2 (g) + 3 H 2 (g) → 2 NH 3 (g) How many moles of NH 3 can be produced by the complete reaction of 4.0 moles of N 2 ? 4.0 mol N 2 x mol N 2 mol NH 3 1 2 = 8.0 moles NH 3 “Mole Ratio” conversion step

10. Lets take a look at another example. N 2 (g) + 3 H 2 (g) → 2 NH 3 (g) How many moles of N 2 are needed to react with 6.0 moles of H 2 ? 6.0 mol H 2 x mol H 2 mol N 2 3 1 = 2.0 moles N 2 “Mole Ratio” conversion step

11. A stoichiometry example with mass relationships. N 2 (g) + 3 H 2 (g) → 2 NH 3 (g) What mass of NH 3 can be produced by the complete reaction of 15.0 g of H 2 ? 15.0 g H 2 x mol H 2 mol NH 3 2.02 2 = 84.4 g NH 3 mole H 2 g H 2 1 x 3 x mol NH 3 g NH 3 1 17.04