Solving a Stoichiometry Problem 1.Balance the equation. 2.Convert given to moles. 3.Determine which reactant is limiting. 4.Use moles of limiting reactant and mole ratios to find moles of desired product. 5.Convert from moles to grams, molecules or Liters.

Practice Test (Ch. 9) 1. How many moles of aluminum chloride (AlCl 3 ) would be produced from 0.12 moles of hydrochloric acid (HCl)? Use Mole Ratio (Balanced Equation) 0.12 mol HCl= mol AlCl 3 mol HCl mol AlCl 3 X Al + 6 HCl  2 AlCl 3 +3 H mol AlCl 3 mol

Practice Test (Ch. 9) 2. If you wanted to completely react 5.0 moles of Aluminum, how many moles of hydrochloric acid (HCl) would be needed? Use Mole Ratio (Balanced Equation) 5.0 mol Al= mol HCl mol Al mol HCl X Al + 6 HCl  2 AlCl 3 +3 H mol HCl mol Al

Practice Test (Ch. 9) 3. How many grams of hydrochloric acid would be needed to completely react 35.8 g of aluminum foil? Convert given to moles 35.8 g Al= g HCl g Al mol Al X 2 Al + 6 HCl  2 AlCl 3 +3 H g Al gHCl Use Periodic Table x _________ g HCl Units don’t match mol Al mol HCl 6 2 X Units still don’t match 1 mol HCl g HCl Use Periodic Table Units Match = 145 Set up Mole Ratio

Practice Test (Ch. 9) 4. How many grams of aluminum would be needed to produce 67.2 dm 3 of hydrogen gas? Convert given to moles 67.2 dm 3 H 2 = g Al dm 3 H 2 mol H 2 x 2 Al + 6 HCl  2 AlCl 3 +3 H dm 3 H 2 gAl 1 mole = 22.4 dm x _________ g Al Units don’t match mol H 2 mol Al 3 2 x Units still don’t match 1 mol Al g Al Use Periodic Table Units Match = Set up Mole Ratio

Practice Test (Ch. 9) 5. How many molecules of carbon dioxide (CO 2 ) would be produced by completely reacting 8.00 grams of oxygen gas (O 2 ) with carbon monoxide (CO)? Convert given to moles 8.00 g O 2 = molec.CO 2 g O 2 mol O 2 x 2 CO (g) + O 2 (g)  2 CO 2 (g) 8.00 g O 2 molec.CO 2 Use Periodic Table x ________ molec.CO 2 Units don’t match mol O 2 mol CO 2 12 x Units still don’t match 1 mol CO 2 molec. CO 2 1 mol = 6.02 x molecules 6.02 x Units Match = 3.01 x Set up Mole Ratio

Practice Test (Ch. 9) 6. What volume in L of oxygen gas (O 2 ) would react with 6.0 L of carbon monoxide gas (CO)? Convert given to moles 6.0 L CO = __________ L O 2 L CO mol CO x 2 CO (g) + O 2 (g)  2 CO 2 (g) 6.0 L CO L O 2 1 mole = 22.4 L x ________ L O 2 Units don’t match mol CO mol O 2 12 x Units still don’t match 1 mol O 2 L O 2 1 mol = 22.4 L 22.4 Units Match = 3.0 Set up Mole Ratio

Practice Test (Ch. 9) 7. What volume in L of ammonia gas (NH 3 ) would be produced from 14.0 g of nitrogen (N 2 ) at STP? Convert given to moles 14.0 g N 2 = ________ L NH 3 g N 2 mol N 2 x N 2(g) + 3 H 2 (g)  2 NH 3 (g) 14.0 g N 2 L NH 3 1 mole = Molar mass (periodic table) x ________ L NH 3 Units don’t match mol N 2 mol NH 3 12 x Units still don’t match 1 mol NH 3 L NH 3 1 mol = 22.4 L 22.4 Units Match = 22.4 Set up Mole Ratio

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) a. The limiting reactant Ideal situation (From Bal.Eqn.) CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) Reactants Compare the two reactants from balance equation to moles given for each reactant in the problem. O2O2 CH 4 = 21 Moles given in Problem 6.0 mol CH mol O 2 O2O2 CH 4 = = is less than 2 so… moles O 2 in given problem is the limiting reagent.

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) b. The reactant in excess Ideal situation (From Bal.Eqn.) CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) Reactants Compare the two reactants from balance equation to moles given for each reactant in the problem. O2O2 CH 4 = 21 Moles given in Problem 6.0 mol CH mol O 2 CH 4 O 2 = = is greater than 0.50 so… moles CH 4 in given problem is the excess reagent. = 0.50

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) c. The moles of carbon dioxide (CO 2 ) produced. ExcessLimiting 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: Start with the limiting reagent 8.0 mol O 2 = ________ mol CO 2 x c. The moles of carbon dioxide (CO 2 ) produced. Use Mole Ratio (Bal. Equation) 2 mol O 2 mol CO Identify what you want to find

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) d. How many grams of excess reactant left over? ExcessLimiting 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: Start with the limiting reagent 8.0 mol O 2 = ________ mol CH 4 x d. How many grams of excess reactant left over ? Use Mole Ratio (Bal. Equation) 2 mol O 2 mol CH Identify what you want to find 1 st find out how much excess gets used up. Amount Used up

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) d. How many grams of excess reactant left over ? ExcessLimiting d. How many grams of excess reactant left over ? Excess Reagent (original amount) mol CH Amount Used up 6.0 mol CH 4 - = 2.0 mol CH 4 Excess moles Left over

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) d. How many grams of excess reactant left over? ExcessLimiting 2.0 mol CH 4 = ________ g CH 4 x d. How many grams of excess reactant left over ? Use molar mass (Periodic table) 1 mol CH 4 g CH mole = Molar mass (Periodic table) grams of excess reactant sig.figs.

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) e. How many grams of water will theoretically be produced fro this reaction? ExcessLimiting 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: Start with the limiting reagent 8.0 mol O 2 = ________ g H 2 O x e. How many grams of water will theoretically be produced fro this reaction? Use Mole Ratio (Bal. Equation) 2 mol O 2 mol H 2 O Identify what you want to find x 1 mol H 2 O g H 2 O Theoretical Yield 1 mole = molar mass (Periodic Table) 144.2

Solving a Stoichiometry Problem 8.If 6.0 moles of methane is mixed with 8.0 moles of O 2, and the mixture is ignited, determine: CH 4 (g) + 2 O 2 (g)  CO 2 (g) +2 H 2 O (l) f. Determine the % yield if the actual amount of water produced during this reaction is g. ExcessLimiting % Yield = Theoretical Yield Actual Yield = g g from previous Problem X 100 = 90.15%