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I’m hiring!

I’m hiring!. Homework Graders Pay = 1 extra credit point/10 papers graded Qualifications : No TUs, BD, LD Availability before/after school or 5 th period lunch. No nepotism/cronyism will be tolerated. HOMEWORK DUE MIErCOLES. If you haven’t done so already, read chapter 3!

jeremy-benjamin
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I’m hiring!

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  1. I’m hiring! Homework Graders • Pay = 1 extra credit point/10 papers graded • Qualifications: • No TUs, BD, LD • Availability before/after school or 5th period lunch. • No nepotism/cronyism will be tolerated

  2. HOMEWORK DUE MIErCOLES • If you haven’t done so already, read chapter 3! • P114 - 115: #22, #32, #34

  3. Stoichiometry The quantitative study of chemical reactions

  4. Use stoichiometry to answer these questions: How much product will form from a given amount of reactants? How much of the reactants is necessary to form a given amount of product?

  5. Stoichiometric Steps

  6. Step 1 • Predict products of a reaction if they are not given to you • Balance the coefficients of the reaction

  7. Step 2 • Use molar conversion to change whatever is given (volume, mass or concentration) to moles

  8. Step 3 • Use the molar ratio from the balanced reaction to convert the moles of what is given to the moles of what’s asked for.

  9. Step 4 • Use conversion factors (moles  mass, volume or M) to change the moles of what is asked for to the proper unit

  10. Calculate the volume of NH3 formed at STP when 5.0 kg of H2 react with excess N2 to form NH3

  11. Calculate the number of molecules of oxygen gas required to burn 3.0 g of C5H10O5

  12. Calculate the mass of solid product formed when 18.4 g of MgBr2 is combined with a solution containing excess K2CO3.

  13. Limiting Reactant • The reactant that gets used up • The reactant that determines the amount of product formed

  14. Excess Reactant • The reactant that Does Not get used up

  15. When I give you quantities of more than one reactant:  You must figure out which one is limiting

  16. 3A + 2B  A3B2Which reactant is limiting? • Do Step 1 and then Step 2 for both A & B. • Pick A (your chemistry grade?) • Use the molar ratio that relates A to B to determine how much of B would be needed to completely use up the moles of A • If there are more than enough moles of B, A is limiting • If there not enough moles of B, then B is limiting • Use limiting reactant for steps 3 & 4

  17. Calculate the mass of glucose (C6H12O6) formed when 880 g of carbon dioxide is combined with 720 g of water in photosynthesis

  18. Calculate the mass of BaSO4 formed when 104 g of BaCl2 is combined with 250 mL 1.00 M K2SO4

  19. How to make a BLT sandwich: 2 LL (lettuce leaves) 5 BS (bacon slices) 3 TS (tomato slices) 2 PB (pieces bread) + + +

  20. So reaction is: • 2 PB + 3 TS + 5 BS + 2 LL  1 BLT 1 BLT

  21. Masses of reactants + product: • 1 PB = 50.0 g • 1 TS = 60.0 g • 1 BS = 20.0 g • 1 LL = 5.0 g • 1 BLT = 390.0 g

  22. How many BLTs? • PB = 3,356.7 g • TS = 4,789.2 g • BS = 2,789.4 g • LL = 789.2 g Get answer in significant digits and then round down to whole number of BLTs.

  23. Theoretical Yield • The amount determined through stoichiometry • The amount solved for on paper

  24. Experimental Yield • The amount obtained in the lab • Actual yield

  25. Percent yield • % Yield = (Exp/Theo) x 100 %

  26. 68 g NH3 was obtained when 140 g of N2 reacts with excess H2. Calculate percent yield.

  27. 510 g PH3 was obtained when 0.62 kg of P4 reacts with excess H2. Calculate percent yield.

  28. 4.61 g of lead(II)iodide was obtained when 66.2 g of lead(II)nitrate was added to 750 ml 0.10 M potassium iodide. Calculate the % yield.

  29. Calculate the volume of oxygen gas at STP required to burn 12 kg of erythrose (C4H8O4)

  30. Determine the volume of NH3 formed at STP when 2.0 x 1027 molecules N2 reacts with 4.0 kg of H2:

  31. Determine the volume of O2 released at STP when 32 kg of Fe2O3 is purified making Fe & O2

  32. Calculate the mass of solid product formed when 41.6 g of barium chloride is added to 250 ml of 0.40 M potassium sulfate giving a 50.0 % yield:

  33. Calculate the mass of solid product formed when 2.00 g of calcium bromide is added to 250 ml of 0.40 M sodium sulfate:

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