7#$$$$$2 RRRRb llxR G*q$G0GGq)GGGGGGGreat Expectations and Preview for Exam #2 Chemistry 141 Autumn Semester 1994 Part I. Review. You should be able to do all the questions on exam #1 Part II. You should be able to balance oxidation-reduction reactions: What atom has been oxidized? What atom has been reduced? Definitions of oxidation and reduction 1. Balance the following reactions in acidic solution: A) MnO4- + Fe2+ Mn2+ + Fe3+ B) C6H8O6 + BrO3- Br- + C6H6O6 + H2O 2. Balance the following reaction in basic solution: Cl2 Cl- + ClO3- You should be able to carry out calculations based on these oxidation reduction reactions: 3. For reaction 1a, how many grams of Mn+2 will be formed from excess permanganate ion and 4.2 grams of iron(II) ions? Part III. You should be able to carry out calculations based on limiting reagents. 4. You combust 25 grams of butane (C4H10) with 23 grams of O2. How much water will you get from the combustion? (recall that oxidation of hydrocarbons give carbon dioxide and water has products). 5. In reaction #4 you get 3.7 grams of water. What is your percent yield for the reaction? 6. You have added 25 mL of 0.20M silver nitrate solution to 57 mL of .15M sodium bromide solution. Write the equation and predict the insoluble material that is formed. How much precipitate will you get from this reaction? 7. How many mL of 0.25M HCl are needed to neutralize 37 mL of 0.036M NaOH? 7a. Outline the procedure in detail for making 2.0 liters of a 1.00 M HNO3 solution from a concentrated stock solution of 70.4% (w/w) HNO3 (d = 1.423 g/ml). Part IV. Gas Law Problems. You should be able to carry out gas law problems and discuss basic notions involved in gas law theories. 8. What are the assumptions behind the concept of an ideal gas? 9. You are on a new planet, and they have used other calculational modes. On this new planet, the standard condition is accepted as: 820 torr for P; 6 quarts for V, 2 for number of moles, and temperature as 400K. What will be the gas law constant for this planet? 10. Essence of skunk is C4H10S. The material making up lemon smell has a formula C10H16. If Prof. King opens bottles of each in the front of the room, which odor will reach you first (assume they are both in the gas phase). How much faster will the winning odor reach you? 11. Explain how a barometer works. 12. You generate hydrogen gas by reacting zinc with HCl to produce hydrogen gas and zinc dichloride. You collect the gas in an evacuated container. If the container holds 3.0L, what will be the pressure of the gas collected at 25C if you start with 6.0 grams of zinc and sufficient HCl to complete the reaction? 13. You should be able to manipulate the ideal gas equation to solve for many different quantities. a. Compare gases under several different conditions: At constant P and n, what is the relationship of V and T? At constant V and T, how does P vary with n? At constant n and T, how does P and V relate? b. Be able to derive the equation showing how you can calculate the molar mass of a gas. 14. The total pressure is 5.11 atmospheres for a gas mixture that consists of 0.307 moles of carbon dioxide and an unknown quantity of methane (CH4) in a 2.59 liter container at 27.0 oC. How many grams of methane are in this mixture? 15. Dichlorodimethylsilane is made by the reaction below, which is carried out at high temperature and in the presence of a catalyst. Si(s) + 2 CH3Cl(g) = (CH3)2SiCl2 (g) Assume you place 0.050 mole of solid silicon in a 16.5 L flask with CH3Cl having a pressure of 885 mm Hg at 25 oC. What is the pressure in the flask (also at 25 oC) on completion of the reaction? 16. What is the pressure of H2 produced in a 2.34 l vessel when 50 ml of a 37.2% (w/w) HCl solution (d = 1.18 g/ml) is reacted with 10.0 g of Mg metal at 25 oC? 2HCl + Mg MgCl2 + H2 17. A concentration of carbon monoxide of 0.4% by volume in air will result in human death in a short time. An idling, untuned car engine with a 300-cu in. displacement can easily produce as much as 0.60 mole of carbon monoxide per minute as a component of its exhaust fumes. If a garage at 27oC has an air volume of 4.1 x 104liters (~1450 cu ft), how long will it take for the sealed garage to reach a lethal concentration of CO? (Neglect the minor effect of total pressure increase; i.e., assume that the pressure remains constant at 1.00 atm and that there is no CO present initially.) u !       !""##$$%%&''(()**++,--B/00122334556XY   s?ghik 4PQ ! " # % \ ^ _ a }   XUV|()/0457;_` @   +PXFs@  efHI34P   A ~  }~x78۳̮ $Yh$  $$  $>$$$ $. $ $$ $$0$0$$9 @   HH(FG(HH(d'@=/88RH -:LaserWriter TimesSymbolE ( ) Preexam#2 Whitney King Whitney King