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Stoichiometry

Stoichiometry. Chapter 9. Stoichiometry. Def: study of mass relationships in chemical reactions Mole conversions Relationship between products and reactants. Stoichiometry. Revolve around balanced equations: Coefficients = # particles # of MOLES of particles

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Stoichiometry

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  1. Stoichiometry Chapter 9

  2. Stoichiometry • Def: study of mass relationships in chemical reactions • Mole conversions • Relationship between products and reactants

  3. Stoichiometry • Revolve around balanced equations: • Coefficients = # particles # of MOLES of particles 2H2 + O2 2H2O 2 moles H2 + 1 mole O2  2 moles H2O

  4. Stoichiometry • MOLAR RATIOS!! • 2H2 + O2 2H2O • Molar ratio of: • H2 : O2? • H2 : H2O • O2 : H2O • Use these as conversion factors!

  5. Mole-Mole Problems • 2H2 + O2 2H2O • How many moles of H2 are required to react with 2.5 mole O2? • How many moles of Al(NO3)3 are produced when .75 mol AgNO3 reacts with Al?

  6. Mass-Mole Problems • Fe2O3 + Al  Al2O3 + Fe • How many moles of Fe are produced when 5.50 g of Fe2O3 reacts? • How many moles of water are required to react with .25 g of Na?

  7. Mole-Mass Problems • Mg + O2 MgO • How many grams of MgO can be produced from 2.95 mol Mg reacting with oxygen? • F2 + KBr  KF + Br2 • What mass of KBr is needed to react with 0.96 mol F2?

  8. Mass-Mass Problems • Sodium phosphate reacts with magnesium nitrate • If you have 3.12g of magnesium nitrate, how many grams of magnesium phosphate will you produce?

  9. Helpful Sites • Mole - Mole • http://science.widener.edu/svb/tutorial/rxnsmolestomolescsn7.html • Mass - Mass • http://science.widener.edu/svb/tutorial/rxnsgramstogramscsn7.html

  10. Limiting Reactants

  11. Limiting Reactants • Amount of products depends on amount of reactants • Car runs because gas reacts with O2 • Out of gas = car doesn’t run • Gas = limiting reactant

  12. Limiting Reactants • Limiting reactant – reactant that limits the amount of product • Amount of product will ONLY be amount made from limiting reactant • Excess reactant– reactant that is not used up completely

  13. Finding the Limiting Reactant • Balance the equation • Pick 1 product and calculate the amount of product produced from both reactants • Reactant that produced the smallest amount of product is limiting reactant

  14. More about Limiting Reactants • Fe + S  FeS • 650. g Fe reacts with 650. g S, what is the LR? • What is the mass of sulfur in excess? • http://www.chemcollective.org/applets/stoich.php

  15. Finding the Limiting Reactant • Cu + AgNO3 Cu(NO3)2 + Ag • If 3.1 mol Cu and 3.1 mol AgNO3 react, what is the limiting reactant? • How many grams of Ag will be produced? • Mass excess reactant unreacted?

  16. Percent Yield • Amount you calculate isn’t what you always produce • Lab errors • Theoretical Yield – amount produced based on calculations

  17. Percent Yield • Actual Yield – amount of product “actually” obtained from lab • Percent Yield – percent of product you actually recovered in lab

  18. Percent Yield • % Yield = actual yield x 100 theoretical yield

  19. Percent Yield • Pb(NO3)2 + KI  PbI2 + KNO3 • Determine the % yield if 16.4 g Pb(NO3)2 reacts with 28.5 g KI if 18.3g PbI2 is produced.

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