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Chemistry

Chemistry. Chapter 10 Stoichiometry. Stoichiometry. Mass and amount relationships between reactants and products in a chemical reaction Requires a balanced chemical equation (molar ratios are necessary). Solving Stoichiometry Problems. List what you know Set up the problem

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Chemistry

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  1. Chemistry Chapter 10 Stoichiometry

  2. Stoichiometry • Mass and amount relationships between reactants and products in a chemical reaction • Requires a balanced chemical equation (molar ratios are necessary)

  3. Solving Stoichiometry Problems • List what you know • Set up the problem • Always begin with a balanced equation • Calculate and verify

  4. Mass-to-Mass Problem Solving • Always begin with a balanced chemical equation • Use the molar mass of the given substance to convert from mass of given (g) to amount of given (mol) • Use the mole ratio of coefficients from the balanced chemical equation to change from amount of a given to amount of unknown • Use the molar ratio of unknown to convert from amount of unknown to mass of unknown

  5. Practice • Look at Sample Problem 10B (page 353) • Practice Problems 1-3

  6. Using Density with Stoichiometry • Volume can be converted to mass if the density is known (or mass to volume) • Example: If the density of a compound is 5.92 g/mL and it has a volume of 52.7 mL, what is the mass?

  7. Practice • Sample Problem 10C on page 355 • Practice Problems 1-2

  8. Calculating Atoms or Formula Units • Avagadro’s number (6.022 x 1023) can be used • 1 mole of substance = 6.022 x 1023 atoms or formula units

  9. Reactants Combine in Specific Whole-Number Ratios • When a chemical reaction occurs, the reactants are seldom present in ratios of amounts equal to their whole ratios • Excess reactant: reactant that will not be completely used up in a reaction that goes to completion • Limiting reactant: reactant that is consumed completely in a reaction that goes to completion

  10. Selecting the Limiting Reactant • In industry, the limiting reactant is normally the more expensive, and is completely used up in the reaction • Ex: O2 is the excess reactant in the reaction that produces apple cider vinegar. Why?

  11. Determining the Limiting Reactant • Look at Sample Problem 10D on page 359 • Practice problems 1-2, page 360

  12. A Chemical Equation tells what COULD happen • Theoretical Yield: the mass of products expected from stoichiometric calculations • Actual Yield: the mass of product actually obtained (normally less than expected- Why?) • Chemical equilibrium: condition where the forward reaction occurs at the same speed as the reverse reaction, and all reactants and products are present

  13. Percentage Yield • Rate of actual yield to the theoretical yield multiplied by 100 percentage yield = actual yield/theoretical yield *100 • Describes reaction efficiency • Percentage yield can be used to predict actual yield • Sample Problem 10E, page 363 • Practice Problems 1-2, page 364 • Sample Problem 10F, page 365

  14. Homework • Read 367-374 and answer the section review questions 1-7

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