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Solving a Stoichiometry Problem

Solving a Stoichiometry Problem. Balance the equation. Convert given to moles. Determine which reactant is limiting. Use moles of limiting reactant and mole ratios to find moles of desired product. Convert from moles to grams, molecules or Liters. Practice Test (Ch. 9).

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Solving a Stoichiometry Problem

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

  2. Practice Test (Ch. 9) 2Al + 6 HCl 2 AlCl3 + 3 H2 6 2 1. How many moles of aluminum chloride (AlCl3) would be produced from 0.12 moles of hydrochloric acid (HCl)? mol AlCl3 0.12 mol Use Mole Ratio (Balanced Equation) mol AlCl3 0.12 mol HCl = mol AlCl3 0.040 X mol HCl

  3. Practice Test (Ch. 9) 2 6 2Al + 6 HCl 2 AlCl3 + 3 H2 2. If you wanted to completely react 5.0 moles of Aluminum, how many moles of hydrochloric acid (HCl) would be needed? 5.0 mol Al HCl mol Use Mole Ratio (Balanced Equation) mol HCl 5.0 mol Al = mol HCl 15 X mol Al

  4. Units don’t match Units Match Units still don’t match Practice Test (Ch. 9) 6 2 2Al + 6 HCl 2 AlCl3 + 3 H2 3. How many grams of hydrochloric acid would be needed to completely react 35.8 g of aluminum foil? g HCl 35.8 g Al Set up Mole Ratio Use Periodic Table Convert given to moles mol Al 1 mol HCl x _________ g HCl 35.8 g Al = g HCl X 26.98 g Al mol Al Use Periodic Table g HCl 36.46 = 145 X 1 mol HCl

  5. Units don’t match Units Match Units still don’t match Practice Test (Ch. 9) 3 2 2Al + 6 HCl 2 AlCl3 + 3 H2 4. How many grams of aluminum would be needed to produce 67.2 dm3 of hydrogen gas? g Al 67.2 dm3 H2 Set up Mole Ratio 1 mole = 22.4 dm3 Convert given to moles mol H2 1 mol Al x _________ g Al x 67.2 dm3 H2 = g Al 22.4 dm3 H2 mol H2 Use Periodic Table g Al 26.98 = x 53.96 1 mol Al

  6. Units don’t match Units Match Units still don’t match Practice Test (Ch. 9) 2CO(g) + O2 (g)2 CO2 (g) 1 2 5. How many molecules of carbon dioxide (CO2) would be produced by completely reacting 8.00 grams of oxygen gas (O2) with carbon monoxide (CO)? molec. CO2 8.00 g O2 Set up Mole Ratio Use Periodic Table Convert given to moles mol O2 1 mol CO2 x 8.00 g O2 x ________ molec.CO2 = molec.CO2 32.00 g O2 mol O2 1 mol = 6.02 x 1023 molecules molec. CO2 6.02 x 1023 = x 3.01 x 1023 1 mol CO2

  7. Units don’t match Units Match Units still don’t match Practice Test (Ch. 9) 2 2CO(g) + O2 (g)2 CO2 (g) 1 6. What volume in L of oxygen gas (O2) would react with 6.0 L of carbon monoxide gas (CO)? L O2 6.0 L CO Set up Mole Ratio 1 mole = 22.4 L Convert given to moles mol CO 1 mol O2 x x ________ L O2 6.0 L CO = __________ L O2 22.4 L CO mol CO 1 mol = 22.4 L L O2 22.4 = x 3.0 1 mol O2

  8. Units don’t match Units Match Units still don’t match Practice Test (Ch. 9) 1 N2(g) + 3 H2 (g)2 NH3 (g) 2 7. What volume in L of ammonia gas (NH3) would be produced from 14.0 g of nitrogen (N2) at STP? L NH3 14.0 g N2 Set up Mole Ratio 1 mole = Molar mass (periodic table) Convert given to moles mol N2 1 mol NH3 x x ________ L NH3 14.0 g N2 = ________ L NH3 28.0 g N2 mol N2 1 mol = 22.4 L L NH3 22.4 = x 22.4 1 mol NH3

  9. O2 = CH4 1 Solving a Stoichiometry Problem Reactants 1 CH4 CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) 2 O2 Compare the two reactants from balance equation to moles given for each reactant in the problem. 8.0 8.0 mol O2 • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: 6.0 6.0 mol CH4 a. The limiting reactant Ideal situation (From Bal.Eqn.) Moles given in Problem 1.33 = = 1.33 is less than 2 so… moles O2in given problem is the limiting reagent.

  10. CH4 = O2 Solving a Stoichiometry Problem Reactants 1 CH4 CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) 2 O2 Compare the two reactants from balance equation to moles given for each reactant in the problem. 8.0 8.0 mol O2 • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: 6.0 6.0 mol CH4 b. The reactant in excess Ideal situation (From Bal.Eqn.) Moles given in Problem = = 0.50 = 0.75 0.75 is greater than 0.50 so… moles CH4in given problem is the excess reagent.

  11. x Solving a Stoichiometry Problem Excess Limiting CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) 2 1 • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: c.The moles of carbon dioxide (CO2) produced. c.The moles of carbon dioxide (CO2) produced. Identify what you want to find Start with the limiting reagent mol CO2 8.0 mol O2 4.0 = ________ mol CO2 mol O2 Use Mole Ratio (Bal. Equation)

  12. x Solving a Stoichiometry Problem Excess Limiting 1 CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) 2 • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: d. How many grams of excess reactant left over? d. How many grams of excess reactant left over ? Identify what you want to find 1st find out how much excess gets used up. Start with the limiting reagent mol CH4 8.0 mol O2 4.0 = ________ mol CH4 mol O2 Amount Used up Use Mole Ratio (Bal. Equation)

  13. 4.0 mol CH4 Amount Used up Solving a Stoichiometry Problem Excess Limiting CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) 6.0 mol CH4 • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: d. How many grams of excess reactant left over ? d. How many grams of excess reactant left over ? - = 2.0 mol CH4 Excess Reagent (original amount) Excess moles Left over

  14. x Solving a Stoichiometry Problem Excess Limiting CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: d. How many grams of excess reactant left over ? d. How many grams of excess reactant left over? 1 mole = Molar mass (Periodic table) 2 sig.figs. 16.05 g CH4 2.0mol CH4 32.10 32 = ________ g CH4 1mol CH4 grams of excess reactant. Use molar mass (Periodic table)

  15. x x Solving a Stoichiometry Problem Excess Limiting CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) 2 2 • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: e. How many grams of water will theoretically be produced fro this reaction? e. How many grams of water will theoretically be produced fro this reaction? Identify what you want to find 1 mole = molar mass (Periodic Table) Start with the limiting reagent mol H2O 18.02 g H2O 8.0 mol O2 = ________ g H2O 1 mol H2O mol O2 Use Mole Ratio (Bal. Equation) Theoretical Yield 144.16 144.2

  16. = = = 90.15% Solving a Stoichiometry Problem Excess Limiting CH4 (g) + 2 O2 (g)CO2 (g) + 2 H2O (l) • If 6.0 moles of methane is mixed with 8.0 moles • of O2, and the mixture is ignited, determine: f. Determine the % yield if the actual amount of water produced during this reaction is 130.0 g. 130.0 g Actual Yield % Yield X 100 X 100 Theoretical Yield 144.2 g from previous Problem

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