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STOICHIOMETRY

STOICHIOMETRY. Mole-Mole Mole- Mass Mass-Mass. STOICHIOMETRY. - the study of the quantitative aspects of chemical reactions. Moles reactant. Moles product. STOICHIOMETRY CALCULATIONS. Stoichiometric factor. Coef. Want Coef. given. Mole -Mole Problems. Moles of the

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STOICHIOMETRY

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  1. STOICHIOMETRY • Mole-Mole • Mole-Mass • Mass-Mass

  2. STOICHIOMETRY - the study of the quantitative aspects of chemical reactions.

  3. Moles reactant Moles product STOICHIOMETRY CALCULATIONS Stoichiometric factor Coef. Want Coef. given

  4. Mole -Mole Problems • Moles of the • Given Substance Moles of the Unknown Substance Conversion Factor: Coefficients from the balanced equation

  5. Example Problem • 2HCl + Fe = FeCl2 + H2 How many mole of HCl are need to react with 6 mole of Fe? 2HCl 1 Fe 6 molFeX = 12 mol HCl

  6. Mole -Mass Problems (2 step) • Moles of the • Given Substance ¸ Mass of the given Substance X Conversion Factor: Molar mass of the given

  7. Mass product Mass reactant Moles reactant Moles product STOICHIOMETRY CALCULATIONS Molar mass Unknown Molar mass given Stoichiometric factor

  8. Example Problem • 2HCl + Fe = FeCl2 + H2 How many grams of HCl are need to react with 6 mole of Fe? 2HCl 1 Fe 6 molFeX = 12 mol HCl 36 g HCl 1 mol = 432g 12 mol HCl X

  9. Mass -Mass Problems (3 step) • Mass of the • Given Substance Mass of the Unknown Substance Conversion Factors:Molar mass of each, and Coefficients from the balanced equation

  10. Mass product Mass reactant Moles reactant Moles product STOICHIOMETRY CALCULATIONS Molar mass Unknown Molar mass given Stoichiometric factor

  11. = 1 molFe How many grams of HCl are need to react with 56 g of Fe? • 2HCl + Fe = FeCl2 + H2 1mol 56 g Fe 56 g of Fe X 2HCl 1 Fe = 2 mol HCl 1 molFeX 36 g HCl 1 mol = 72g HCl 2 mol HCl X

  12. PROBLEM: If 454 g of NH4NO3 decomposes, how much N2O and H2O are formed? What is the theoretical yield of products? STEP 1 Write the balanced chemical equation NH4NO3 ---> N2O + 2 H2O

  13. 454 g of NH4NO3 --> N2O + 2 H2O STEP 2 Convert mass reactant (454 g) --> moles STEP 3 Convert moles reactant (5.68 mol) --> moles product

  14. STEP 3 Convert moles reactant --> moles product Relate moles NH4NO3 to moles product expected. 1 mol NH4NO3 --> 2 mol H2O Express this relation as the STOICHIOMETRIC FACTOR.

  15. 454 g of NH4NO3 --> N2O + 2 H2O STEP 3 Convert moles reactant (5.68 mol) --> moles product = 11.4 mol H2O produced

  16. 454 g of NH4NO3 --> N2O + 2 H2O STEP 4 Convert moles product (11.4 mol) --> mass product Called the THEORETICAL YIELD ALWAYS FOLLOW THESE STEPS IN SOLVING STOICHIOMETRY PROBLEMS!

  17. 454 g of NH4NO3 --> N2O + 2 H2O STEP 5 How much N2O is formed? Total mass of reactants = total mass of products 454 g NH4NO3 = ___ g N2O + 204 g H2O mass of N2O = 250. g

  18. 454 g of NH4NO3 --> N2O + 2 H2O STEP 6 Calculate the percent yield If you isolated only 131 g of N2O, what is the percent yield? This compares the theoretical (250. g) and actual (131 g) yields.

  19. 454 g of NH4NO3 --> N2O + 2 H2O STEP 6 Calculate the percent yield

  20. PROBLEM: Using 5.00 g of H2O2, what mass of O2 and of H2O can be obtained? 2 H2O2(liq) ---> 2 H2O(g) + O2(g) Reaction is catalyzed by MnO2 Step 1: moles of H2O2 Step 2: use STOICHIOMETRIC FACTOR to calculate moles of O2 Step 3: mass of O2

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