ESSENTIAL QUESTION: WHAT CAN A BALANCED EQUATION TELL YOU ABOUT A REACTION? Please Place cell phones in cell phone caddy. Warm-Up: Pre/post Test

CHEMICAL QUANTITIES Chapter 12

WHAT CAN A BALANCED EQUATION TELL YOU ABOUT A REACTION? N 2 + 3H 2  2NH 3 1. Used to calculate how much product can be produced. 2. It can be used to interpret different quantities of : a. Atoms: there are eight atoms on the product side and eight on the reactant side b. Molecules: one molecule of Nitrogen combines with 3 molecules of Hydrogen; the ratio will always be 3:1

N 2 + 3H 2  2NH 3 c. Moles: The coefficients indicate how many moles of reactants and products you have; this is the most important information the equations provides. 1 mole of Nitrogen combines with 3 moles of Hydrogen to form 2 moles of ammonia d. Mass: Law of conservation of mass e. Volume: at STP you can 22.4 liters of nitrogen reacts with 67.2 liters of hydrogen to form 44.8 liters of ammonia

HOW CAN A MOLE RATIO BE USED? 1. The mole ratios taken from a balanced chemical equation can be used as a conversion factor N 2 + 3H 2  2NH 3

2. How many moles of H are needed to prepare 312 moles of ammonia?

3. If you want to make 250 moles of ammonia, how many moles of nitrogen would you need?

ESSENTIAL QUESTION: WHAT CONVERSION FACTORS ARE NEEDED WHEN DOING MOLE-MASS PROBLEMS? Please Place cell phones in cell phone caddy. Warm-Up: Coming Next….

BALANCE AND SOLVE H 2 + O 2  H 2 O 2 How many moles of H 2 O 2 can you make if you have 3.75 moles of O 2 ?

HOW CAN THE MOLE RATIO BE USED TO SOLVE A PROBLEM INVOLVING MASS? If you see grams in the problem you are going to need to calculate the molar mass. 1. Begin with your given (circle it). 2. Calculate the molar mass of your atom or compound. 3. You will need several conversion factors: a. Molar mass b. Mole ratio from the balanced equation 4. Label all your steps and cross out units that cancel each other out. 5. Finish be ending with the unit you are being asked for (put a box around it).

N 2 + 3H 2  2NH 3 6. What mass of NH 3 can be made from 1221 grams of H 2 and excess N 2?

Fe 2 O 3 + 2Al  2Fe + Al 2 O 3 7. How many grams of Al would you need to react with 135 grams of FeO 3 ?

CHECK-OUT: 1.What conversion factors are needed when doing mole-mass problems? 2.

ESSENTIAL QUESTION: WHAT CONVERSION FACTORS DO YOU NEED WHEN COMPLETING VOLUME-MOLE PROBLEMS? PROBLEMS INVOLVING PARTICLES? Please Place cell phones in cell phone caddy. Warm-Up: How many grams of H 2 O 2 can be made from 100 grams of O 2 ? H 2 + O 2  H 2 O 2

HOW CAN THE MOLE RATIO BE USED TO SOLVE A PROBLEM INVOLVING VOLUME? 1. Must be at STP: 1 ATM, kPa or 760 mmHg and 0 C or 273 K 2. Begin with your given (circle it). 3. You will need several conversion factors: a. 1 mole occupies 22.4 Liters b. Mole ratio from the balanced equation 4. Label all your steps and cross out units that cancel each other out. 5. Finish be ending with the unit you are being asked for (put a box around it).

6. What volume of H 3 PO 4 forms when 5.6 L POCl 3 completely reacts? POCl 3 + 3H 2 O  H 3 PO 4 + 3HCl

7. What volume of H 3 PO 4 forms when 5.6 L POCl 3 completely reacts? POCl 3 + 3H 2 O  H 3 PO 4 + 3HCl

HOW CAN MOLE RATIOS BE USED TO SOLVE PROBLEMS INVOLVING PARTICLES? 1. Begin with your given (circle it). 2. You need several conversion factors 6.02 X particles = 1 mole Molar mass = 1 mole Mole ratio from the balanced equation 3. Labeling all your steps and cross out units that cancel each other out. 4. Finish be ending with the unit you are being asked for (put a box around it).

C 5 H 12  C 5 H 8 + 2H 2 5. How many grams of C 5 H 8 form from 1.89 X molecules of C 5 H 12 ?

6. How many molecules of hydrogen gas are formed from 25 grams of C 5 H 8 ?

ESSENTIAL QUESTION: HOW IS THE LIMITING REAGENT DETERMINED? Please Place cell phones in cell phone caddy. Warm-Up: How many liters of H 2 O 2 can be made from 3.87 X molecules of O 2 ? H 2 + O 2  H 2 O 2

HOW CAN LIMITING REACTANT BE DETERMINED? 1. Balance the chemical equation 2. Calculate the molar mass of the reactants 3. Use the molar mass and mole ratios to calculate the theoretical yield 4. See which quantity is smaller; the smaller one is you limiting reactant

PCl 3 + H 2 O  H 3 PO 3 + HCl 5. What is the limiting reactant and the theoretical yield of phosphorus acid, if 225 grams of PCl 3 is mixed with 123 grams of H 2 O?

ESSENTIAL QUESTION: HOW IS THE PERCENTAGE YIELD DETERMINED? Please Place cell phones in cell phone caddy. Warm-Up: What is the limiting reagent if 32 grams of H 2 and 62 grams of O 2 are used to make H 2 O 2 ? H 2 + O 2  H 2 O 2

HOW CAN PERCENTAGE YIELD BE DETERMINED? 1. Balance the chemical equation 2. Calculate the molar mass of the reactants 3. Use the molar mass and mole ratios to calculate the theoretical yield 4. Use the formula to calculate percentage yield Actual yield/Theoretical Yield X 100

5. Determine the limiting reactant, the theoretical yield and the percentage yield if 14.0 g N 2 are mixed with 9.0 grams H 2 and 16.1 NH 3 form.

CHECK-OUT: How is the percentage yield determined?