1. TOPIC: Predicting amounts of reagents needed or amounts of products made Do Now:

2. Coefficients in Chemical Equations in front ofNumbers in front of formulas called coefficients –Microscopic: Coefficients represent numbers of individual atoms or molecules –Macroscopic: Coefficients give mole ratios! –Moles  connected to mass

3. Coefficients in Balanced Equations MOLE-MOLE word problems: convert from moles of one substance to moles of another substance

4. 2 C 2 H 6 + 7 O 2  4 CO 2 + 6 H 2 O How much CO 2 will be produced if 4 moles of C 2 H 6 are consumed? 1) Start with balanced chemical equation 2) Problem will ask how many moles/liters given will yield certain amount something else 3) Use a proportion to compare old mole/liter amounts to the new mole/liter amounts

5. 2 C 2 H 6 4 CO 2 2 C 2 H 6 + 7 O 2  4 CO 2 + 6 H 2 O CO 2 C 2 H 6 How much CO 2 will be produced if 4 moles of C 2 H 6 are consumed? 4 moles C 2 H 6 = X moles CO 2 X = 8 moles CO 2

6. 2 C 2 H 6 6 H 2 O 2 C 2 H 6 + 7 O 2  4 CO 2 + 6 H 2 O H 2 O C 2 H 6 How much H 2 O will be produced in the combustion of 5 moles of C 2 H 6 ? 5 moles C 2 H 6 = X moles H 2 O X = 15 moles H 2 O

7. 2 C 2 H 6 7 O 2 2 C 2 H 6 + 7 O 2  4 CO 2 + 6 H 2 O oxygen C 2 H 6 How much oxygen will react with 5 moles of C 2 H 6 ? 5 moles = X moles X = 17.5 moles O 2

8. Gas-Phase Equations coefficients in equations represent ratio of volumes of gases involved in rxn volume-volume word problems: rxns where ALL reactants & products are gases  volume unit (liter/milliliter) doesn’t matter as long as constant throughout

9. N 2 (g) + 3 H 2 (g)  2 NH 3 (g) How much hydrogen gas will react with 15 liters of nitrogen gas? _________ 15 L N 2 (g) = X L H 2 (g) _________ X = 45 L H 2 (g) 1

10. Mass-Volume Problems REMINDER: 1 mole any gas occupies same volume as any other gas (At STP = 22.4 L/mol) REMINDER: 1 mole = gram formula mass –CO 2 = 12 + 16 + 16 = 44 g/mol

11. What volume of Cl 2 (g) measured at STP is produced when 7.65g HCl (aq) reacts with MnO 2 MnO 2 (s) + 4HCl(aq)  MnCl 2 (aq) + Cl 2 (g) + 2H 2 O(l) 1. CONVERT TO MOLES 7.65g HCl mol=.2125 mols HCl 36 g HCl 2. Set up ratio 4 = 1=.053125 mols Cl 2.2125 X 3. Convert Moles to Liters.053125 mols Cl 2 22.4 L = 1.19 L 1 mol

12. What mass of NH 3 (g) is produced when 2.15L of H 2 (g) measured at STP reacts? 3H 2 (g) + N 2 (g)  2NH 3 (g) 1.Set up Ratio 3 = 2= 1.43 L NH 3 2.15 X 2. Convert L to Moles 1.43 L mol=.064 mol NH 3 22.4 L 3. Convert Moles to grams.064 mol 17 g = 1.09 g mol