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Stoichiometry. Section 11.1 Defining Stoichiometry Section 11.2 Stoichiometric Calculations Section 11.3 Limiting Reactants Section 11.4 Percent Yield. Click a hyperlink or folder tab to view the corresponding slides. Exit. Chapter Menu. Section 11.1 Defining Stoichiometry.

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  1. Stoichiometry Section 11.1Defining Stoichiometry Section 11.2Stoichiometric Calculations Section 11.3Limiting Reactants Section 11.4Percent Yield Click a hyperlink or folder tab to view the corresponding slides. Exit Chapter Menu

  2. Section 11.1 Defining Stoichiometry • Describethe types of relationships indicated by a balanced chemical equation. reactant:the starting substance in a chemical reaction • Statethe mole ratios from a balanced chemical equation. stoichiometry mole ratio The amount of each reactant present at the start of a chemical reaction determines how much product can form. Section 11-1

  3. Particle and Mole Relationships • Chemical reactions stop when one of the reactants is used up. • Stoichiometryis the study of quantitative relationships between the amounts of reactants used and amounts of products formed by a chemical reaction. Section 11-1

  4. Particle and Mole Relationships (cont.) • Stoichiometry is based on the law of conservation of mass. • The mass of reactants equals the mass of the products. Section 11-1

  5. Particle and Mole Relationships (cont.) Section 11-1

  6. Particle and Mole Relationships (cont.) • A mole ratio is a ratio between the numbers of moles of any two substances in a balanced equation. • The number of mole ratios that can be written for any equation is (n)(n – 1) where n is the number of species in the chemical reaction. Section 11-1

  7. A B C D Section 11.1 Assessment Which of the following is a correct mole ratio for the following equation? 2Al(s) + 3Br2(l) → 2AlBr3(s) A.2 mol Al : 3 mol Br B.3 mol Br2 : 2 mol Al C.2 mol AlBr3 : 1 mol Br2 D.2 mol Br : 2 mol Al Section 11-1

  8. A B C D Section 11.1 Assessment How many mole ratios can be written for the following reaction? 4H2(g) + O2(g) → 2H2O(l) A.6 B.4 C.3 D.2 Section 11-1

  9. Section 11.2 Stoichiometric Calculations • Listthe sequence of steps used in solving stoichiometric problems. chemical reaction:a process in which the atoms of one or more substances are rearranged to form different substances • Solvestoichiometric problems. The solution to every stoichiometric problem requires a balanced chemical equation. Section 11-2

  10. Using Stoichiometry • All stoichiometric calculations begins with a balanced chemical equation. 4Fe(s) + 3O2(g)  2Fe2O3(s) Section 11-2

  11. Using Stoichiometry (cont.) • Steps to solve mole-to-mole, mole-to-mass, and mass-to-mass stoichiometric problems • Complete Step 1 by writing the balanced chemical equation for the reaction. • To determine where to start your calculations, note the unit of the given substance. • If mass (in grams) of the given substance is the starting unit, begin your calculations with Step 2. • If amount (in moles) of the given substance is the starting unit, skip Step 2 and begin your calculations with Step 3. Section 11-2

  12. Using Stoichiometry (cont.) 3.The end point of the calculation depends on the desired unit of the unknown substance. • If the answer must be in moles, stop after completing Step 3. • If the answer must be in grams, stop after completing Step 4. Section 11-2

  13. Using Stoichiometry (cont.) Section 11-2

  14. A B C D Section 11.2 Assessment A chemical reaction equation must be ____ in order to make stoichiometric calculations. A.measured B.controlled C.balanced D.produced Section 11-2

  15. A B C D Section 11.2 Assessment How many moles of CO2 will be produced in the following reaction if the initial amount of reactants was 0.50 moles? 2NaHCO3 → Na2CO + CO2 + H2O A.0.25 B.0.3 C.0.5 D.1.0 Section 11-2

  16. Section 11.3 Limiting Reactants • Identifythe limiting reactant in a chemical equation. • Identifythe excess reactant, and calculate the amount remaining after the reaction is complete. • Calculatethe mass of a product when the amounts of more than one reactant are given. molar mass:the mass in grams of one mole of any pure substance Section 11-3

  17. Section 11.3 Limiting Reactants (cont.) limiting reactant excess reactant A chemical reaction stops when one of the reactants is used up. Section 11-3

  18. Why do reactions stop? • Reactions proceed until one of the reactants is used up and one is left in excess. • The limiting reactant limits the extent of the reaction and, thereby, determines the amount of product formed. • The excess reactantsare all the leftover unused reactants. Section 11-3

  19. Why do reactions stop? (cont.) • Determining the limiting reactant is important because the amount of the product formed depends on this reactant. Section 11-3

  20. Calculating the Product when a Reactant is Limiting • S8(l) + 4Cl2(g) → 4S2Cl4(l) • 200.0g S and 100.0g Cl2 • Determine which is the limiting reactant • mole of reactants: 1.1410 mol CI2; 0.7797 mol S8 • mole ratios determine that for every 1 mol of S8, 1.808 mol CI2 are available • mole ratio from equation is 4 mol Cl2 : 1 mol S8 • Chlorine is limiting since there are less moles available than required by the equation. Section 11-3

  21. Calculating the Product when a Reactant is Limiting (cont.) • Calculating the amount of product formed • Multiply the amount of limiting reactant (Cl2) by the mole ratio relating S2Cl2 to Cl2. • 190.4g S2Cl2 form Section 11-3

  22. Calculating the Product when a Reactant is Limiting (cont.) • Analyzing the excess reactant • Moles reacted • Multiply the moles of Cl2 used by the mole ratio relating S8 to Cl2. • 0.3525 mol S8 • Mass reacted. • Multiply moles reacted by molar mass. • 90.42g of S8 • Excess remaining. • 200.0g – 90.42g = 109.6 g S8 in excess Section 11-3

  23. Calculating the Product when a Reactant is Limiting (cont.) • Using an excess reactant can speed up the reaction. • Using an excess reactant can drive a reaction to completion. Section 11-3

  24. A B C D Section 11.3 Assessment The mass of the final product in a chemical reaction is based on what? A.the amount of excess reactant B.the amount of limiting reactant C.the presence of a catalyst D.the amount of O2 present Section 11-3

  25. A B C D Section 11.3 Assessment What is the excess reactant in the following reaction if you start with 50.0g of each reactant? P4(s) + 5O2(g) → P4O10(s) A.O2 B.P4 C.Both are equal. D.unable to determine Section 11-3

  26. Section 11.4 Percent Yield • Calculatethe theoretical yield of a chemical reaction from data. process:a series of actions or operations • Determinethe percent yield for a chemical reaction. theoretical yield actual yield percent yield Percent yield is a measure of the efficiency of a chemical reaction. Section 11-4

  27. How much product? • Laboratory reactions do not always produce the calculated amount of products. • Reactants stick to containers. • Competing reactions form other products. Section 11-4

  28. How much product? (cont.) • The theoretical yieldis the maximum amount of product that can be produced from a given amount of reactant. • The actual yield is the amount of product actually produced when the chemical reaction is carried out in an experiment. • The percent yieldof a product is the ratio of the actual yield expressed as a percent. Section 11-4

  29. Percent Yield in the Marketplace • Percent yield is important in the cost effectiveness of many industrial manufacturing processes. Section 11-4

  30. A B C D Section 11.4 Assessment The amount of product that can be produced from a given amount of reactants based on stoichiometric calculations is: A.actual yield B.percent yield C.theoretical yield D.stoichiometric yield Section 11-4

  31. A B C D Section 11.4 Assessment You calculate the theoretical yield of a chemical reaction starting with 50.0g of reactant is 25.0g of product. What is the percent yield if the actual yield is 22.0g of product? A.88% B.44% C.50% D.97% Section 11-4

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