CHM-201 General Chemistry and Laboratory I Unit #3 Unit Test Version A April 18, 2018 - CORRECTED Directions: Complete this test and pass in the answer sheet only. On the answer sheet, be sure to enter your student ID and fill in the appropriate bubbles. Record your answers unambiguously ambiguous answers are wrong. Do not cross out answers. You may use the test and/or the examination booklet for your work. The version is already recorded on your answer sheet. 1. The reaction that represents the standard enthalpy of formation for benzene (C 6H 6) is: A) 6 C(diamond) + 3 H 2(g) C 6H 6(l) B) 6 C(graphite) + 6 H(g) C 6H 6(l) C) C 6H 6(l) + 15 / 2 O 2(g) 6 CO 2(g) + 3 H 2O(g) D) 6 C(graphite) + 3 H 2(g) C 6H 6(l) E) C 6H 6(l) 6 C(graphite) + 3 H 2(g) 2. A sample of a gas occupies 1.40 10 3 ml at 25 C and 760 mmhg. What volume will it occupy at the same temperature and 380 mmhg? A) 2,800 ml B) 2,100 ml C) 1,400 ml D) 1,050 ml E) 700 ml 3. The atmospheric pressure on a rainy day was measured at 661 mmhg. What is this pressure expressed in units of atmospheres? A) 0.661 atm B) 1.15 atm C) 0.981 atm D) 0.760 atm E) 1.02 atm 4. Calculate the standard enthalpy change for the reaction 4A + 2B 2AB + A 2 Given: 2A + B A 2B 2A 2B 2AB + A 2 ΔH = -25.0 kj/mol ΔH = 35.0 kj/mol A) 95.0 kj/mol B) 60.0 kj/mol C) 15.0 kj/mol D) 10.0 kj/mol E) 45.0 kj/mol 5. How many liters of oxygen gas at 153 C and 0.820 atm can be produced by the decomposition of 22.4 g of solid KClO 3? (The other decomposition product is solid potassium chloride.) A) 0.085 L B) 3.0 L C) 4.20 L D) 7.79 L E) 11.7 L
6. Calculate the mass of 1.5 L of CO 2(g) at 120 C and 790 mmhg pressure. A) 0.048 g B) 2.1 g C) 2.7 g D) 5.1 g E) 12 g 7. A 1.17 g sample of an alkane hydrocarbon gas occupies a volume of 674 ml at 28 C and 741 mmhg. Alkanes are known to have the general formula C nh 2n+2. What is the molecular formula of the gas in this sample? A) CH 4 B) C 2H 6 C) C 3H 8 D) C 4H 10 E) C 5H 12 8. A gas evolved during the fermentation of sugar was collected. After purification its volume was found to be 25.0 L at 22.5 C and 702 mmhg. How many moles of gas were collected? A) 0.95 mol B) 1.05 mol C) 12.5 mol D) 22.4 mol E) 724 mol 9. The enthalpy of combustion of acetylene C 2H 2 is described by C 2H 2(g) + 5 / 2 O 2(g) 2CO 2(g) + H 2O(l), ΔH rxn= 1299 kj/mol. Calculate the enthalpy of formation of acetylene, given the following enthalpies of formation ΔH f[co 2(g)] = 393.5 kj/mol ΔH f[h 2O(l)] = 285.8 kj/mol A) 216 kj/mol B) 226 kj/mol C) 236 kj/mol D) 246 kj/mol E) None of the above 10. An exothermic reaction causes the surroundings to A) decrease in temperature. B) become acidic. C) increase in temperature D) release CO 2. E) expand.
11. What is the pressure (mmhg) of the sample of gas trapped in the open-tube mercury manometer shown below if atmospheric pressure is 742 mmhg and h = 16.7 cm? A) 375 mmhg B) 475 mmhg C) 575 mmhg D) 675 mmhg E) None of the Above 12. Which of these gases will have the lowest density if they are all measured at the same temperature and pressure? A) Br 2 B) CClF 3 C) CCl 4 D) C 2H 2 E) CCl 2F 4 13. Find the standard enthalpy of formation of ethylene, C 2H 4(g), given the following data: heat of combustion of C 2H 4(g )= 1411 kj/mol; ΔH f[co 2(g)] = 393.5 kj/mol; ΔH f[h 2O(l)] = 285.8 kj/mol. A) 52 kj/mol B) 87 kj/mol C) 731 kj/mol D) 1.41 10 3 kj/mol E) 2.77 10 3 kj/mol 14. Given H 2(g) + ½ O 2(g) H 2O(l) (ΔH = 286 kj/mol), determine the standard enthalpy change for the reaction 2H 2(g) + O 2(g) 2H 2O(l). A) ΔH = 286 kj/mol B) ΔH = +286 kj/mol C) ΔH = 572 kj/mol D) ΔH = +572 kj/mol E) ΔH = 143 kj/mol 15. Select True or False: The specific heats of water and iron are 4.184 and 0.444 J/g C, respectively. When equal masses of water and iron both absorb the same amount of heat, the temperature increase of the water will be 2.42 times greater than that of the iron. A) True B) False
16. Determine the pressure of the gas trapped in the apparatus shown below when the atmospheric pressure is 696 mmhg. A) 45 mmhg B) 651 mmhg C) 695 mmhg D) 741 mmhg E) 760 mmhg 17. A beaker contains 115 g of ethanol at 18.2 C. If the ethanol absorbs 1125 J of heat without losing heat to the surroundings, what will be the final temperature of the ethanol? The specific heat of ethanol is 2.46 J/g C. A) 4.08 C B) 14.1 C C) 18.4 C D) 22.2 C E) 36.4 C 18. 0.820 mole of hydrogen gas has a volume of 2.00 L at a certain temperature and pressure. What is the volume of 0.125 mol of this gas at the same temperature and pressure? A) 0.0512 L B) 0.250 L C) 0.305 L D) 4.01 L E) 19.5 L 19. Calculate the heat required when 2.50 mol of A reacts with excess B and A 2 B according to the reaction: 2A + B + A 2B 2AB + A 2 Given: 2A + B A 2B 2A 2B 2AB + A 2 ΔH = -25.0 kj/mol ΔH = 35.0 kj/mol A) 10.0 kj B) 12.5 kj C) 25.0 kj D) 35.0 kj E) 62.5 kj 20. Which of the following has a ΔH f = 0 kj/mol? A) CO 2(g) B) O 3(g) C) Cl - (aq) D) NH 3(aq) E) I 2(s)
21. What volume of oxygen gas will be produced by the complete decomposition of 21.8g of solid KClO 3 181 C and 1.17 atm? 2KClO 3(s) 2KCl(s) + 3O 2(g) A) 1.51 L B) 2.26 L C) 5.67 L D) 17.0 L E) 8.50 L 22. Find ΔH rxn for the reaction 2Na(s) + 2H 2O(l) 2NaOH(aq) + 2H 2(g). ΔH f (NaOH(aq)) = 426.8 kj/mol; ΔH f (H 2O(l)) = 285.5 kj/molooo A) 284.6 kj B) 282.6 kj C) 280.6 kj D) 278.6 kj E) None of the above