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Warm-up 5/13/13

Warm-up 5/13/13. From the Activity last class: 1 M 2 + 3 C 2 → 2 MC 3 What is the ratio of M 2 /MC 3 ? What is the ratio of C 2 /MC 3 ? How could you find these without actually counting paperclips?

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Warm-up 5/13/13

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  1. Warm-up 5/13/13 From the Activity last class: 1M2 + 3C2 → 2MC3 • What is the ratio of M2/MC3? • What is the ratio of C2/MC3? • How could you find these without actually counting paperclips? • How many MC3 compounds could be produced from 24 M2? (assume you have an unlimited supply of C2)

  2. I. Introduction • Stoichiometry: Describes the quantitative relationships among substances in a chemical reaction • Derived from the Greek words stoicheion "element" and metron "measure" • Why is this important? • Describes how much will be made from a chemical reaction (or how much is needed).

  3. II. Map

  4. One Step Problems1. Mole – Mole • What is a mole ratio? A comparison of the coefficients from a balanced chemical equation. • Example: • Start with a balanced reaction: 2Al2O3 → 4Al + 3O2 Use the coefficientsto determine the mole ratios.

  5. ____CO2+ ____LiOH____Li2CO3 + ____H2O 1) How many moles of LiOH are required to react with 20 mol of CO2? 2) How many moles of Li2CO3 will be produced from 3.5 moles of LiOH?

  6. _____ H2 + _____ N2  _____NH3 1) How many moles of H2 are required to form 5.0 moles of NH3? 2) Find the number of moles of N2 needed to react completely with 4.52mol of H2.

  7. _____ H2 + _____ N2  _____NH3 3) How many moles of N2 will be needed to form 6.0 moles of NH3? 4) 10 moles of H2 will form how many moles of NH3?

  8. IV. Multiple Step Problems • For these problems you will need: • Balanced Equation • Map • UNITS!

  9. _____ KClO3 _____KCl + _____O2 1. Potassium chlorate decomposes to produce potassium chloride and oxygen. How many grams of potassium chlorate are required to produce 0.00953 moles of oxygen?

  10. 2 KClO3 2 KCl + 3 O2 2. Using the same balanced equation above, how many moles of potassium chlorate are needed to produce 250 grams of oxygen.

  11. 2 KClO3 2 KCl + 3 O2 3. If you begin with 5.0g of potassium chlorate, what is the mass of potassium chloride that will be produced?

  12. _____NH4NO3  _____N2 + _____O2+_____ H2O 1) Ammonium nitrate is found in fertilizers and high explosives. It is unstable and decomposes into several gases, nitrogen and oxygen, as well as water. The rapid expansion of the gases produces the explosive force. Find the mass of water produced from 125.0 grams of the ammonium nitrate

  13. _____ZnS + _____O2 _____ZnO + _____ SO2 The white solid found in some sunblock is zinc oxide. This is produced by burning zinc sulfide in oxygen. 2) To produce 10.0 grams of zinc oxide, how many grams of zinc sulfide are used?

  14. VI. Percent Yield • Definition:   • the ratio of the actual yield to the theoretical yield • A measure of the efficiency of a reaction • Equation:

  15. VI. Percent Yield 1. Lead nitrate can be decomposed by heating. What is the percent yield of the decomposition reaction if 9.9g of Pb(NO3)2 are heated to give 5.5g of PbO? 2Pb(NO3)2 → 2PbO + 4NO2 + O2

  16. VI. Percent Yield 2. Hydrogen gas is produced when zinc reacts with hydrochloric acid. If the actual yield of this reaction is 85%, how many grams of zinc are needed to produce 112L of H2 at STP? Zn + 2HCl → ZnCl2 + H2

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