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Stoichiometry

Stoichiometry. Ch.10. (10-1) Stoichiometry. Mass & amt relationships b/w reactants & products Conversions b/w grams & moles Always begin w/ a balanced eq. !. Mass to Mol Reminder. Convert 3.5 g of NaOH to mols NaOH List known 3.5 g NaOH Calculate molar mass

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Stoichiometry

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  1. Stoichiometry Ch.10

  2. (10-1) Stoichiometry • Mass & amt relationships b/w reactants & products • Conversions b/w grams & moles • Always begin w/ a balanced eq.!

  3. Mass to Mol Reminder Convert 3.5 g of NaOH to mols NaOH • List known 3.5 g NaOH • Calculate molar mass 22.99 g/mol Na + 16 g/mol O + 1.01 g/mol H = 40 g/mol • Set up problem & solve 3.5 g NaOH x 1 mol NaOH = 0.09 mol NaOH 40 g NaOH

  4. Mol to Mass Reminder How many grams are in 6.4 mols O2? • List known 6.4 mols O2 • Calculate molar mass (2) (16 g/mol O) = 32 g/mol O2 • Set up problem & solve 6.4 mols O2x 32 g O2 = 204.8 g O2 1 mol O2

  5. Mol to Mol Reminder If 2.00 mol N2 is reacting w/ a sufficient amt of H2, how many mols of NH3 will be produced? N2 + H2 NH3 • Balance the chemical eq. N2 + 3H2 2 NH3

  6. Mol to Mol Reminder • Find the mole ratio 1 mol N2 : 2 mol NH3 • Set up problem (begin w/ known) & solve 2.00 mol N2 x 2 mol NH3 = 4 mol NH3 1 mol N2

  7. Conversions g of A  mol of A  mol of B  g of B Mole ratio (coeff.from bal.eq.) Molar Mass (from PT) Molar Mass (from PT)

  8. Mass to Mass Practice How many grams of H2O are produced when 13 g O2 combine w/ sufficient H2? H2 + O2 H2O • Balance the chemical eq. 2 H2 + O2 2 H2O

  9. Mass to Mass Practice • Calculate molar mass of known & unknown O2 = 32 g/mol H2O = 18.02 g/mol • Find mole ratio 1 mol O2 : 2 mol H2O

  10. Mass to Mass Practice 4. Set up problem (begin w/ known) & solve 13 g O2 x 1 mol O2 x 2 mol H2O x 18.02 g H2O 32 g O2 1 mol O2 1 mol H2O = 14.63 g H2O

  11. Using Density • Density (D) = mass (m) / volume (V) • Units: g/mL • Convert from g  mL or mL  g

  12. Density Practice Calculate the mass of LiOH used to obtain 1500 mL of water. (Hint: DH2O = 1.00 g/mL) CO2 + 2LiOH  Li2CO3 + H2O • Start w/ known & use density to convert into grams 1500 mL H2O x 1.00 g H2O 1 mL H2O

  13. Density Practice • Proceed w/ mass to mass calc. 1500 mL H2O x 1.00 g H2O x 1 mol H2O x 1 mL H2O 18.02 g H2O 2 mol LiOH x 23.95 g LiOH = 3989 g LiOH 1 mol H2O 1 mol LiOH

  14. (10-2) Excess Reactant • Extra left over after rxn • Limiting reactant: completely consumed • Limits amt of other reactants used • Determines max amt of product

  15. Limiting Reactant Practice CO combines w/ H2 to produce CH3OH. If you had 152.5 g CO & 24.5 g H2 what mass of CH3OH could be produced? • Write a bal. eq. CO + 2 H2 CH3OH

  16. Limiting Reactant Practice • Convert reactants to mols present 152.5 g CO x 1 mol CO = 5.444 mol CO present 28.01 g CO 24.50 g H2 x 1 mol H2= 12.1 mol H2present 2.02 g H2

  17. Limiting Reactant Practice • Using the reactants mol ratio, find how many mols needed 12.1 mol H2 x 1 mol CO = 6.06 mol CO needed 2 mol H2 • CO present is not enough to react w/ all the H2, so CO is limiting

  18. Limiting Reactant Practice 4. Use limiting reactant to set up stoich. 5.444 mol CO x 1 mol CH3OH x 32.05 g CH3OH 1 mol CO 1 mol CH3OH = 174.5 g CH3OH

  19. Theoretical Yield • Calculated max amt of product possible • Stoich. w/ limiting reactant • What should happen • Actual yield: measured amt of product experimentally produced • What does happen

  20. Percentage Yield • How efficient a rxn is • How close actual is to theoretical • Should be 100% • % yield = actual x 100 theoretical

  21. % Yield Practice When 0.835 mol LiOH is reacted w/ excess KCl, the actual yield of LiCl is 16 g. What is the % yield? LiOH + KCl  LiCl + KOH

  22. % Yield Practice 1. Calculate the theor. yield 0.835 mol LiOH x 1 mol LiCl x 42.44 g LiCl = 35.4 g LiCl 1 mol LiOH 1 mol LiCl • Calculate the % yield % yield = act. X 100 = 16 g LiCl x 100 = 45 % theor. 35.4 g LiCl

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