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Chapter 8 Stoichiometry

Chapter 8 Stoichiometry. What is Stoichiometry? -deals with quantities of materials consumed and produced in chemical reactions What info is needed for stoichiometry problems? Balanced chemical equation Mole ratio- conversion factor that relates amounts in moles of any 2 substances

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Chapter 8 Stoichiometry

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  1. Chapter 8Stoichiometry What is Stoichiometry? -deals with quantities of materials consumed and produced in chemical reactions What info is needed for stoichiometry problems? • Balanced chemical equation • Mole ratio- conversion factor that relates amounts in moles of any 2 substances • Molar mass- conversion factor that relates mass of a substance to the amount of moles of that substance

  2. Stoichiometry Examples Oxygen can be produced by the decomposition of potassium chlorate. In the process potassium chloride is also produced. • Write a balanced equation. 2KClO3 3O2 + 2KCl • If you had 11.3 moles of potassium chlorate, how many moles of oxygen would be produced? • How many grams of potassium chlorate would be produced from 9.30 moles of oxygen?

  3. Con. c) How many moles of potassium chloride will be produced in the reaction if 94.7 g of oxygen are produced? d) How many grams of oxygen would be produced when 49.89 g of potassium chlorate decomposes?

  4. Using Density with Stoichiometry What is density? D=mass/volume Example: In the space shuttles, the CO2 that the crew exhales is removed from the air by a reaction with canisters of lithium hydroxide. On average, each astronaut exhales about 20.0 moles of CO2 daily. Water and lithium carbonate are produced in this reaction. What volume of water will be produced when this amount of CO2 reacts with excess Lithium hydroxide. ( Hint: the density of water is about 1.00g/ml.)

  5. Con. Magnesium burns in oxygen to produce magnesium oxide. How much magnesium will burn in presence of 189 ml of oxygen. The density of oxygen is 1.429 g/L. 2 Mg + O2 2MgO

  6. Limiting and Excess Reactants Limiting Reactant- reactant that is used up first Excess Reactant- reactant that is not completely used up How can the limiting reactant be determined? Set up 2 mole problems. The smaller amount is the limiting reactant.

  7. Limiting/excess example Carbon monoxide can be combined with hydrogen to produce methanol, CH3OH. Methanol is used as an industrial solvent, as a reactant in synthesis, and as a clean-burning fuel for some racing cars. If you had 152.5 kg CO and 24.50 kg H2, how many kilograms of methanol would be produced? CO (g) + 2H2(g)  CH3OH(l)

  8. Another example Ammonia,NH3, is used throughout the world as a fertilizer. To manufacture ammonia, nitrogen is combined with hydrogen in a synthesis reaction. If 92.7 kg of nitrogen and 265.8 kg of hydrogen are used, which is the limiting reactant?

  9. Theoretical Yield • calculated maximum amount of product possible Actual yield- amount of product actually created Percent yield= actual yield• 100 theoretical yield

  10. Percent Yield Example Determine the limiting reactant and the percent yield if 14.0 g of nitrogen react with 3.15 g of hydrogen to give an actual yield of 14.5 g of NH3.

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