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Stoichiometry Limiting Reagent (Reactant)

CHEM 106. Stoichiometry Limiting Reagent (Reactant). Dr. Ron Rusay. https://phet.colorado.edu/sims/html/reactants-products-and-leftovers/latest/reactants-products-and-leftovers_en.html. Limiting Reagent An Ice Cream Sundae. The Balanced Equation (Recipe). The Stuff to be Mixed Together:.

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Stoichiometry Limiting Reagent (Reactant)

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  1. CHEM 106 Stoichiometry Limiting Reagent (Reactant) Dr. Ron Rusay https://phet.colorado.edu/sims/html/reactants-products-and-leftovers/latest/reactants-products-and-leftovers_en.html

  2. Limiting ReagentAn Ice Cream Sundae The Balanced Equation (Recipe) The Stuff to be Mixed Together: ??????

  3. Limiting ReagentAn Ice Cream Sundae What’s left? What’s totally consumed? 8 scoops ice cream 6 cherries 100 mL syrup

  4. QUESTION Making a cheese sandwich can be represented by the equation (recipe): 2 Bread (Bd) + Cheese (Ch) → Bd2ChWhat would you expect a sandwich to look like? A B C D https://phet.colorado.edu/sims/html/reactants-products-and-leftovers/latest/reactants-products-and-leftovers_en.html

  5. Making a different type of cheese sandwich can be represented by the equation: Bd2 + 2Ch → 2BdCh What would you expect a sandwich of this type to look like? QUESTION A B C D https://phet.colorado.edu/sims/html/reactants-products-and-leftovers/latest/reactants-products-and-leftovers_en.html

  6. QUESTION The planned menu at DVC’s soon to open Chemistry Café has a sandwich formula for meat lovers, BdM2Ch, where M is the meat of your choice in the sandwich. What might the sandwich likely have in it? • 1 pannini, 2 grams of prosciutto, 1 gram of mortadella • 2 slices of bread, 2 pieces of salami, 1 piece of swiss cheese • 1 slice of bread, 2 pieces of pastrami, 1 piece of asiago cheese • 1 loaf of bread, 2 kg of bologna, 1 lb of cream cheese

  7. QUESTION The planned DVC menu also has the “Chem Club” with 3 pieces of bread, two thick slices of roast beef, and 2 slices of gruyere cheese. What is the correct formula to place on the printed menu? • Bd2M3Ch2 • Bd3M2Ch3 • Bd2M2Ch2 • Bd3M2Ch2 https://phet.colorado.edu/sims/html/reactants-products-and-leftovers/latest/reactants-products-and-leftovers_en.html

  8. QUESTION The sous chef at the Chemistry Café has a loaf of sourdough bread with 33 slices and a package of cheddar cheese with 15 slices. She is making sandwiches that have 2 pieces each of both bread and cheese. How many sandwiches can she make? • 30 • 16 • 15 • 7

  9. Limiting Reagent https://phet.colorado.edu/sims/html/reactants-products-and-leftovers/latest/reactants-products-and-leftovers_en.html

  10. QUESTION • Consider the reaction between AB and B2 in the gas phase: • Select the correct statement about this reaction. • The balanced equation for the reaction is AB + B2→ AB3. • B) AB and B2 are present in “stoichiometric” (equivalent molar) amounts at the start of the reaction to consume all of both. • C) AB is the limiting reagent. • D) The product of the reaction is A2B.

  11. ANSWER • Consider the reaction between AB and B2 in the gas phase: • Select the correct statement about this reaction. • The balanced equation for the reaction is AB + B2→ AB3. • B) AB and B2 are present in “stoichiometric” (equivalent molar) amounts at the start of the reaction to consume all of both. • C) AB is the limiting reagent. • D) The product of the reaction is A2B.

  12. QUESTION

  13. ANSWER

  14. http://www.cnafun.moa.gov.cn/zl/tjzl/201306/P020130620619849846691.pdfhttp://www.cnafun.moa.gov.cn/zl/tjzl/201306/P020130620619849846691.pdf QUESTION

  15. Answer B. False World capacity (kcal) = 3.04 x 1019 J x 1cal/4.184J x 1kcal/1000cal World capacity (kcal) = 7.26 x 1015kcal (per year) World demand = 2700 kcal/ person x 1/day x 365 days/yr = 6.9 x 1015 kcal (per year)

  16. Answer Do you consume more or less than 2700 Cal/day (kcal/day)? B. False What is recommended for your age and relative life style? http://www.cnpp.usda.gov/publications/usdafoodpatterns/estimatedcalorieneedsperdaytable.pdf

  17. Determining a Limiting Reagent • Which one of the reactants has fewer stoichiometrically adjusted moles than the other reactant? The reactant with the smaller value is the limiting reagent. Calculation: • Divide the mass of each reactant by its respective Molar Mass, and then by its Stoichiometric factor from the balanced equation; compare the results. The lowest one is the limiting reagent.

  18. Limiting Reagent Calculation • The reactant present in the smallest molar amount considering stoichiometry limits the mass basis of any reaction. • 2 C8H18(l)+ 25 O2(g)16 CO2(g)+18 H2O(l) • 228 g octane / 114 g/mol = 2 mol octane • 600. g oxygen / 32 g/mol = 18.75 mol oxygen • 2 mol octane / 2 mol (stoich.) = 1 • 18.75 mole oxygen / 25 mol (stoich.) = 0.75

  19. Mass Effects of theLimiting Reagent What amount of octane remains unreacted in the reaction of 600. g of O2 with 228 g of octane? • 600. g O2 x mol O2 /32g O2 x [2mol C8H18 /25mol O2] x 114 g / mol C8H18 = 171 g C8H18 are reacted • 228 g - 171 g = 57 g C8H18 remain unreacted https://phet.colorado.edu/sims/html/reactants-products-and-leftovers/latest/reactants-products-and-leftovers_en.html

  20. QUESTION

  21. ANSWER

  22. Limiting Reagent / Theoretical Yield The limiting reagent governs the theoretical yield of products. For the reaction of 228 g of octane with 600. g of oxygen, what is the theoretical yield of carbon dioxide? 2 C8H18(l)+ 25 O2(g)16 CO2(g)+18 H2O(l) 600. g O2 x mol O2 /32g O2 x 16mol CO2 /25mol O2 x 44g / mol CO2 = 528 g CO2

  23. Percent Yield • A reaction was conducted that theoretically would produce 0.0025 moles of quinine, C20 H24 N2 O2 . The actual amount of isolated quinine was 780 mg. What is the percent yield of quinine? • 324 g/mol x 0.0025 mol = 81g = 810mg(theoretical) • % Yield = 780 mg/ 810 mg x 100 • % Yield = 96%

  24. QUESTION • If a reaction produced 2.45g of Ibogaine, C20H26N2O, a natural product with strong promise in treating heroin addiction, and the theoretical yield was 3.05g, what is the % yield? A) 19.7% B) 39.4% C) 80.3% D) 160.6%

  25. ANSWER • If a reaction produced 2.45g of Ibogaine, C20H26N2O, a natural product with strong promise in treating heroin addiction, and the theoretical yield was 3.05g, what is the % yield? • 19.7% B) 39.4% C) 80.3% D) 160.6% % yield = 2.45g / 3.05g x 100 = 80.3%

  26. Thoughts to Consider How much CO2 do you produce per gallon of gasoline (octane, d= 0.70 g/ml) when gasoline is combusted? How much CO2 do you personally produce from driving every week?…. every month? …. every year? ….from other uses and sources? “Man-made” CO2 directly relates to global warming. How does “man-made” CO2 relate to jobs and the global economy? Why do people in nations in the EU, the U.S., China, Japan & others produce tons more of CO2 than people in under developed or developing nations? Global Warming Questions

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