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27 Sept. 2010

27 Sept. 2010. Objective: SWBAT write, balance, read and interpret chemical equations, and complete mole to mole stoichiometric calculations. Do now: Calculate the mass of just the oxygen in 5.00 grams of water. Agenda. Do now Homework presentation Notes and examples Practice problems

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27 Sept. 2010

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  1. 27 Sept. 2010 • Objective: SWBAT write, balance, read and interpret chemical equations, and complete mole to mole stoichiometric calculations. • Do now: Calculate the mass of just the oxygen in 5.00 grams of water.

  2. Agenda • Do now • Homework presentation • Notes and examples • Practice problems • Homework: p. 112 #56, 57, 59, 63, 66, 68 (OH)

  3. Decoding Chemical Equations • 2H2(g) + O2(g)  2H2O(l)

  4. Balancing Chemical Equations Ex 1. KClO3 KCl + O2 Ex 2. C2H6 + O2  CO2 + H2O

  5. Practice Problems • On your worksheet, practice writing and balancing chemical equations.

  6. Mole Ratios • Coefficients indicate the number of moles (or molecules) of each compound • Ex 1. N2(g) + 3H2(g)  2NH3(g) • How many moles of hydrogen gas react with 1 mole of nitrogen gas? • How many moles of ammonia gas are produced by the reaction of 3 moles of hydrogen gas in excess nitrogen gas?

  7. N2(g) + 3H2(g)  2NH3(g) • How many moles of hydrogen gas are required to react with 15 moles of nitrogen gas? • How many moles of hydrogen gas are required to produce 25.0 moles of ammonia gas? • If 10 moles of nitrogen gas was reacted with 10 moles of hydrogen gas, which would be completely reacted? Which would be excess?

  8. Homework • p. 112 #56, 57, 59, 63, 66, 68 (OH) • Test Thursday (ch. 1, 2, 3)

  9. 28 Sept. 2010 • Take out homework • Objective: SWBAT complete mass to mass stoichiometric calculations. • Do now: Gaseous ammonia reacts with oxygen gas to produce nitrogen monoxide gas and liquid water. How many moles of nitrogen monoxide are produced by the reaction of 0.00300 moles of ammonia in excess oxygen?

  10. Agenda • Do now • Homework check: on ELMO! • Mass to mass stoichiometry examples and practice problems! • Homework: p. 113 #70, 72, 74, 76, 78 (MO)

  11. Mass to mass stoichiometric relationships: Ex 1. The food we eat is degraded in our bodies to provide energy for growth and function. A general equation for this very complex process is: C6H12O6 + 6O2 6CO2 + 6H2O If 856 g of C6H12O6 is consumed by a person over a certain period, what is the mass of CO2 produced?

  12. Example 2 • All alkali metals react with water to produce hydrogen gas and the corresponding alkali metal hydroxide. A typical reaction is that between lithium and water: 2Li(s) + 2H2O(l)  2LiOH(aq) + H2(g) How many grams of Li are needed to produce 9.89 grams of H2?

  13. Example 3 • Methanol (CH3OH) burns in air according to the equation 2 CH3OH + 3O2 2CO2 + 4H2O If 209 g of methanol are used up in the combustion process, what is the mass of H2O produced?

  14. Example 4 • The reaction between nitric oxide and oxygen to form nitrogen dioxide is a key step in photochemical smog formation: 2NO(g) + O2(g)  2NO2(g) How many grams of O2 are needed to produce 2.21 g of NO2?

  15. Homework • p. 113 #70, 72, 74, 76, 78 (MO)

  16. 29 Sept. 2010 • Objective: SWBAT determine limiting reagent, and calculate percent yield. • Do now: Nitrogen monoxide gas reacts with oxygen gas to produce nitrogen dioxide gas. If 5.00 grams of nitrogen monoxide reacts with excess oxygen, how many grams of nitrogen dioxide gas are produced?

  17. Agenda • Do now • Homework check (MO) • Limiting reagent • Percent Yield Homework: p. 113 #82, 84, 86, 90, 92, 94 (SR) Test Monday Review tomorrow

  18. Limiting Reagents Ex 1. • Urea is prepared by reacting ammonia with carbon dioxide: 2NH3(g) + CO2(g) (NH2)2CO(aq) + H2O(l) In one process, 637.2 g of NH3 are treated with 1142 g of CO2. a) Which of the two reactants is the limiting reactant? b) Calculate the mass of (NH2)2CO formed. c) How much excess reagent (in grams) is left at the end of the reaction?

  19. Example 2 • The reaction between aluminium and iron(III) oxide can generate temperatures approaching 3000oC and is used in welding metals: 2Al + Fe2O3 Al2O3 + 2Fe In one process, 124 g of Al are reacted with 601 g of Fe2O3. a) Calculate the mass (in grams) of Al2O3 formed. b) How much of the excess reagent is left at the end of the reaction?

  20. 30 Sept. 2010 • Objective: SWBAT determine limiting reagent, and calculate percent yield. • Do now: TiCl4(g) + 2Mg(l)  Ti(s) + 2MgCl2(l) If 3.54x107 g of TiCl4 are reacted with 1.13x107 g of Mg, calculate the limiting reagent and the theoretical yield of Ti.

  21. Agenda • Do now • Homework check (JMS) • Limiting reagent • Percent Yield Homework: p. 113 #90, 92, 94 (SR) Test Monday

  22. Reaction Yield theoretical yield: the amount of product that would result if all of the limiting reagent reacted. actual yield: amount of product actually obtained from a reaction

  23. Percent Yield Ex 1 • Titanium is a strong, lightweight, corrosion-resistant metal that is used in rockets, aircraft, jet engines and bicycle frames. It is prepared by the reaction of titanium (IV) chloride with molten magnesium between 950oC and 1150oC: • TiCl4(g) + 2Mg(l)  Ti(s) + 2MgCl2(l) 3.54x107 g of TiCl4 are reacted with 1.13x107 g of Mg. a) Calculate the theoretical yield of Ti in grams. g) Calculate the percent yield if 7.91x106 g of Ti are actually obtained.

  24. Ex 2. • Industrially, vanadium metal, which is used in steel alloys, can be obtained by reacting vanadium(V) oxide with calcium at high temperatures: 5Ca + V2O5 5CaO + 2V 1.54x103 g of V2O5 is reacted with 1.96x103 g of Ca. a) Calculate the theoretical yield of V. b) Calculate the percent yield if 803 g of V are obtained.

  25. Homework • Test (ch. 1-3) tomorrow • p. 113 #82, 84, 86, 90, 92, 94 (SR)

  26. On the test • Classification and states of matter • Physical and chemical properties • Measurement, handling numbers • Dimensional analysis • Atomic theory and structure • Atomic number, mass number, isotopes • Molecules and Ions • Chemical formulas and names (incl. acids) • Avogadro’s number, moles, molar mass • % composition by mass • Empirical and molecular formulas • Chemical reactions and equations • Mole to Mole and Mass to Mass Stoichiometry • Limiting reagents, reaction yield

  27. Review Game! • With your partner, solve the problem and show all your work. • Raise your hand when you are done. • First group with the correct answer gets the point and a chance at the bonus point.

  28. An unfortunate tree is carrying on photosynthesis in the forest. One morning, it wakes up with dew on its leaves. The sunshine immediately begins to evaporate the dew. Suddenly, a storm rolls in and a giant wind knocks the tree to the ground. A limb is struck by lighting and partially burns. Over the next year, the remaining parts of the tree rot away. List all the physical changes in one column and the chemical changes in another.

  29. One gallon of gasoline in an automobile’s engine produces on the average 9.5 kg of carbon dioxide. Calculate the annual production of CO2 in kilograms if there are 40 million cars in the US and each car covers a distance of 5000 mi. at a consumption rate of 20 miles per gallon.

  30. A transition metal with 26 protons and 24 electrons forms a bond with a polyatomic ion consisting of phosphorus and four atoms of oxygen with a charge of 3-. • a) What type of bond holds this compound together? • b) Write the name and formula for this compound.

  31. Imagine this compound contains hydrogen instead of iron. • a) What type of compound is it? • b) Write the name and formula for this compound.

  32. Imagine that acid lost one oxygen. Name and write the formula for the newly formed acid.

  33. Calculate the molar mass of this acid, and the percent by mass of each element.

  34. A compound is formed by one carbon atom and four chlorine atoms. • a) What type of bond holds these atoms together? • b) Write the name and formula of this compound.

  35. Carbohydrates contain C, H and O, in which the hydrogen to oxygen ratio is 2:1. A certain carbohydrate contains 40.0% carbon by mass. Calculate the empirical and molecular formulas if the molar mass is about 178 g.

  36. Lysine, an essential amino acid in the human body contains C, H, O and N. In one experiment, the complete combustion of 2.175 g of lysine gave 3.94 g CO2 and 1.89 g H2O. In a separate experiment, 1.873 g of lysine gave 0.436 g NH3. a) Calculate the empirical formula. • b) If the molar mass is about 150 g, calculate the molecular formula.

  37. Hydrogen gas can be prepared by reacting propane gas (C3H8) with steam at about 400oC. The products are carbon monoxide and hydrogen gas. a) Write a balanced equation. • b) How many kilograms of hydrogen gas can be obtained from 2.84x103 kg of propane?

  38. Solid elemental sulfur reacts with a solution of nitric acid to produce a solution of sulfuric acid, nitrogen dioxide gas and water. Write and balance a chemical equation.

  39. When potassium cyanide reacts with acids, a deadly poisonous gas, hydrogen cyanide, is given off. • KCN(aq) + HCl(aq)  KCl(aq) + HCN(g) • If a sample of 0.140 g of KCN is treated with an excess of HCl, calculate the amount of HCN formed, in grams.

  40. Nitric oxide (NO) reacts with oxygen gas to form nitrogen dioxide, a dark brown gas. • In one experiment, 0.866 mol of nitric oxide is mixed with 0.503 mol of oxygen gas. Calculate which is the limiting reagent. How many moles of nitrogen dioxide are produced?

  41. When heated, lithium reacts with nitrogen to form lithium nitride. • What is the theoretical yield of lithium nitride in grams with 12.3 grams of lithium are heated with 33.6 grams of nitrogen? • If the actual yield of lithium nitride is 5.89 grams, what is the percent yield?

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