Chemistry 121 Chapters 5 and 6 Sample Questions Note: These questions are not designed to be a study guide for the exam since they do not represent all of the information presented in these chapters or topic emphasis. However, you should be able to quick answer all of these questions and understand the underlying principles associated with these questions. 1. If 5.0 kJ of energy is added to a 15.5 g sample of water at 10.0oC, the water is: a. b. c. 2. increase in temperature decrease in temperature not change temperature d. e. increase and then decrease in temperature none of the above answers (a-d) is correct -19 oC +6 oC -14 oC d. e. -17 oC +14 oC Two pieces of metal, metal A and metal B, each with the same mass, are heated in a propane flame. Once they both reach 257 oC, they are each placed in a separate bucket containing 20. L of H2O at 5oC. The buckets are allowed to sit for five minutes and then the temperature is measured. Metal A has a specific heat of 3.98 J/g . oC, and metal B has a specific heat of 2.23 J/g . oC. Which of the following statements is true? a. b. c. d. e. 5. all a gas plasma A glass containing 200. g of H2O at 20. oC was placed into a refrigerator. How many degrees does the temperature of the water change after it loses 11.7 KJ of energy? a. b. c. 4. d. e. An endothermic reaction causes the surroundings to: a. b. c. 3. a liquid a solid boiling The bucket of water with metal A will be hotter. The bucket of water with metal B will be hotter. Since the two metals were heated to the same temperature, the buckets of water will be at the same temperature. Bucket A will be 79 oC and bucket B will be 65 oC. Since we don’t know the exact masses of the metals, we cannot determine which bucket will be hotter. For the reaction, C (s) + O2 (g) burned to release 275 kJ of heat? a. 22.3 g b. 0.700 g CO2 (g), ∆H = -393 kJ. How many grams of C(s) must be c. 12.0 g d. 17.9 g e. 8.40 g 6. Consider the following equations: Pb(s) + Pb(s) + H2O(g) + O2(g) Cl2(g) Cl2(g) PbO2(s) PbCl2(s) 2HCl(g) + 1/2O2(g) + 2H2O(g) ∆Ho = -15.80 kJ ∆Ho = -20.52 kJ ∆Ho = +3.27 kJ Calculate ∆Ho for the reaction: PbO2(s) + a. b. c. 7. 4HCl(g) PbCl2(s) -33.05 kJ -11.26 kJ -1.44 d. e. + 2H2O(l) +42.87 kJ -7.99 kJ 2H2SO4(l) + Pb(s) Compound PbO2(s) H2SO4(l) PbSO4(s) H2O(l) a. b. c. -79.5 kJ -131.2 kJ -66.9 kJ d. e. 2PbSO4(s) ∆H fo (kJ/mol) -15.8 -46.5 -52.6 -16.3 -6.5 kJ -28.9 kJ Argon has a density of 1.40 g/L at standard conditions. How many argon atoms are in 1.0 L of argon gas? a. b. c. 9. Cl2(g) Calculate ∆Ho for the reaction PbO2(s) + 8. + 4.7 x 1022 3.4 x 1025 1.5 x 1025 d. e. Given the equation S(s) + true? O2(g) 2.1 x 1022 1.2 x 1024 SO2(g), ∆H = -296 kJ. Which of the following is(are) I. The reaction is exothermic II. When 0.500 mole of sulfur is reacted, 148 kJ of energy is released. III. When 32.0 g of sulfur are burned, 2.96 x 105 J of energy of released. a. I,II, III b. I, III c . I, II d. II, III 10. When methane, CH4, is reacted with oxygen it first produces carbon monoxide and water. If you carry out the reaction and collect 49 L of water vapor at STP, how many moles of CH4 were reacted. Assume a 100% yield of product. a. b. c. 4.4 mol 1.8 mol 2.2 mol d. e. 0.60 mol 1.1 mol 11. How many grams of H2O will be formed when 32.0 g of H2 is mixed with 32.0 g of O2 and allowed to react and form water. a. b. c. 51.0 g 288 g 18.0 g d. e. 36.0 g 64.0 g 12. Consider the reaction below: 2NO(g) + O2(g) 2NO2(g) 100. mL of NO at STP is mixed with 400. mL of O2 at STP. After the reaction goes to completion, calculate the total volume of all the gases present at STP. a. 200. mL b. 250. mL c. 350. mL d. 450. mL e. 500. ML 13. Consider three one-liter flasks labeled A, B, and C that are filled with the gases NO, NO2, and N2O respectively. If all of the flasks are at STP, which flask contains 1.0 mole of gas? a. b. c. Flask A Flask B Flask C d. e. none (A-C) of the flasks have one mole of gas. all (A-C) of the flasks have one mole of gas. 14. A 2.66L container contains He at a pressure of 1.5 atm, and Ar at a pressure of 1.5 atm. The mole fraction of Ar in the container is: a. 0.50 b. 1.0 c. 1.5 d. 0.22 e. 0.56 -75 kJ e. 1.0 x 102 kJ 15. Given the following information: A + 1/2B B + ∆Ho = +50. KJ 2C D C ∆Ho = -25 KJ What is ∆Ho for the reaction? A a. 25 kJ 2D b. 75 kJ c. 0 kJ d. 16. A glass container at a constant temperature and a pressure of 1 atm is filled with x moles of gas. If 2x additional moles of gas are then added to the container, what is the new pressure in the container? a. b. c. 1 atm 2 atm 3 atm d. e. x atm none of the answers (a-d) are correct. 17. Real gases deviate from ideal behavior because of the attractive forces between the gas molecules and a. b. c. d. e. ionization energies molecular vibrations molecular rotations pressures between chemical bonds the actual volume of the molecules 18. Two 100.0 g chunks of metal, metal "A" and metal "B" are placed in an oven at 1000oC for 5 seconds. Assume that there isn't enough time for either chunk of metal to reach 1000oC. Metal A has a specific heat of 1.0 J/g . oC. Metal B has a specific heat of 2.0 J/g . oC. Which of the following statements is true. a. When the chunks of metal are removed from the oven, Metal A will be hotter. b. When the chunks of metal are removed from the oven, Metal B will be hotter. c. When the chunks of metal are removed from the oven, they both will be the same temperature. d. The relative temperatures of the two pieces of metal cannot be predicted. e. none of the answers (a-d) are correct. 19. Which of the following gases would occupy the smallest volume at 25oC and the same pressure? a. 100 g of CH4 b. 100 g of N2O c. 100 g of O3 d. 100 g of N2 e. 100 g of all gases would occupy the same volume under these conditions. 20. All the following statements describe 104 g of gaseous tetrafluorohydrazine, N2F4, at 0ºC and 76 cmHg pressure EXCEPT a. b. c. d. e. one mole of gas. 22.4 L of gas. the amount of gas that contains 28.0 g of nitrogen. the amount of gas that contains 76.0 g of fluorine. the amount of gas that contains 104 x 6.02 x 1023 molecules of N2F4. 21. What is the MOLAR heat of combustion of methanol, CH3OH, if combustion of 1.00 g of methanol causes a temperature rise of 3.68°C in a bomb calorimeter that has a heat capacity of 6.43 kJ/°C? (Formula weight CH3OH = 32.0.) a. b. c. d. e. 55.9 kJ/mol 923 kJ/mol 757 kJ/mol 18.3 kJ/mol 368 kJ/mol