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Chapter 12

Chapter 12. Stoichiometry. Stoichiometry. The branch of chemistry that deals with the mass relationships of elements in compounds and the mass relationships between reactants and products in a chemical reaction. Composition Stoichiometry.

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Chapter 12

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  1. Chapter 12 Stoichiometry

  2. Stoichiometry The branch of chemistry that deals with the mass relationships of elements in compounds and the mass relationships between reactants and products in a chemical reaction.

  3. Composition Stoichiometry • Stoichiometry that deals with the mass relationships of elements in compounds

  4. Reaction Stoichiometry • Stoichiometry involving the mass relationships between reactants and products in a chemical reaction

  5. Equations are the recipes that tell chemists • what amounts of reactants to mix and • what amounts of products to expect. • The quantities of reactants and products -----come from the balanced equation.

  6. When you know the quantity (grams or moles) of one substance in a reaction, you can calculate the quantity of any other substance consumed or created in the reaction.

  7. Calculations using balanced equations are called stoichiometric calculations. For chemists, stoichiometry is a form of bookkeeping.

  8. N2(g) + 3H2(g) 2NH3(g) INTERPRETING CHEMICAL EQUATIONS 1 mol of nitrogen reacts with 3 mol of hydrogen -------to form 2 mol of ammonia.

  9. Reaction – Stoichiometry Problems • Begin with a balanced chemical equation!!!

  10. Mole-Mole Calculations • The coefficients from the balanced equation are used to write conversion factors called mole ratios.

  11. Three of the mole ratios for this equation are 1 mol N2 2 mol NH3 3 mol H2 3 mol H2 1 mol N2 2 mol NH3

  12. Reaction – Stoichiometry Problems • Identify the information given • Identify the unknown, the information you are expected to find. • Given  Unknown

  13. Given amount in moles Mole to Mole Ratio Unknown amount in moles

  14. From balanced equation b mol W xb a molG a x mol G x = mol W Thus a general solution for a mole-mole problem is given by Given Mole ratio Calculated

  15. 2 mol NH3 1 mol N2 How many moles of ammonia are produced when 0.60 mol of nitrogen reacts with hydrogen? 0.60 mol N2 x = 1.20 mol NH3 Given Mole Ratio

  16. Problem • In a spacecraft, the carbon dioxide exhaled by astronauts can be removed by its reaction with lithium hydroxide. • CO2(g) + 2 LiOH(s)  Li2CO3(s) + H2O (l) • How many moles of lithium hydroxide are required to react with 20 moles of CO2, the average amount exhaled by a person each day?

  17. Answer • 20 mole CO2 x 2 mole LiOH 1 mole CO2 = 40 mole LiOH

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