GENERAL CHEMISTRY I CHM201 Unit 3 Practice Test This test is intended to help you get acquainted with the types of questions you will be asked on the Unit Test administered at the end of the unit. The answers are included at the end of the test. Do not pass in your answers to this test. This is optional and will not be graded. Feel free to seek any help you wish on these questions. A mastery of the topics covered in them will assure a good performance on the tests that count. THIS IS NOT THE TAKE HOME TEST. DO NOT PASS IN AN ANSWER SHEET FOR THIS TEST. 1. What will happen to the height (h) of the column of mercury in the manometer shown below if the stopcock is opened? A) h will decrease B) h will not change C) h will increase D) not enough information given to answer the question 2. The atmospheric pressure on a sunny day was measured at 775 mmhg. What is this pressure expressed in units of atmospheres? A) 0.775 atm B) 0.980 atm C) 1.02 atm D) 0.760 atm E) 6.61 atm 3. A sample of oxygen gas has a volume of 545 ml at 35 C. The gas is heated to 151ºC at constant pressure in a container that can contract or expand. What is the final volume of the oxygen gas? A) 750. ml B) 396 ml C) 417 ml D) 267 ml E) 126 ml 4. The temperature of a sample of argon gas in a 365 ml container at 740. mmhg and 25 C is lowered to 12 C. Assuming the volume of the container and the amount of gas is unchanged, calculate the new pressure of the argon. A) 0.468 atm B) 0.931 atm C) 1.02 atm D) 1.54 atm E) 2.03 atm 5. Calculate the volume occupied by 56.5 g of argon gas at STP. A) 22.4 L B) 31.7 L C) 34.6 L D) 1,270 L E) 1,380 L
6. Calculate the mass, in grams, of 2.74 L of CO gas measured at 33 C and 945 mmhg. A) 0.263 g B) 2.46 g C) 3.80 g D) 35.2 g E) 206 g 7. Which of these gases will have the lowest density if they are all measured at the same temperature and pressure? A) H 2 B) CClF 3 C) CO 2 D) C 2 H 6 E) CF 4 8. 1.018 g of Freon-113 gas is trapped in a 145 ml container at 760. mmhg and 50.0 C. What is the molar mass of Freon-113? A) 21.7 g/mol B) 28.8 g/mol C) 46.1 g/mol D) 186 g/mol E) 245 g/mol 9. How many liters of chlorine gas at 25 C and 0.950 atm can be produced by the reaction of 12.0 g of MnO 2 with excess HCl(aq) according to the following chemical equation? MnO 2 (s) + 4HCl(aq) MnCl 2 (aq) + 2H 2 O(l) + Cl 2 (g) A) 5.36 10-3 L B) 0.138 L C) 0.282 L D) 3.09 L E) 3.55 L 10. When active metals such as magnesium are immersed in acid solution, hydrogen gas is evolved. Calculate the volume of H 2 (g) at 30.1 C and 0.85 atm that can be formed when 275 ml of 0.725 M HCl solution reacts with excess Mg to give hydrogen gas and aqueous magnesium chloride. Mg(s) + 2HCl(aq) MgCl 2 (aq) + H 2 (g) A) 3.4 10-3 L B) 2.2 L C) 2.9 L D) 5.8 L E) 11.7 L
11. What is the pressure of the gas trapped in the apparatus shown below when the atmospheric pressure is 745 mmhg? A) 12 mmhg B) 708 mmhg C) 720 mmhg D) 733 mmhg E) 760 mmhg 12. An endothermic reaction causes the system to A) warm up. B) decrease in temperature. C) become acidic. D) release O 2. E) condense. 13. Calculate the amount of heat necessary to raise the temperature of 135.0 g of water from 50.4 C to 85.0 C. The specific heat of water = 4.184 J/g C. A) 1.1 kj B) 10.9 kj C) 16.6 kj D) 19.5 kj E) 48.0 kj 14. Which of the following processes is endothermic, given the following: S(s) + O 2 (g) SO 2 (g) ΔH = 299 kj/mol S(s) + 3/2 O 2 (g) SO 3 (g) ΔH = 395 kj/mol A) 2 S(s) + 2 O 2 (g) 2 SO 2 (g) B) ½ S(s) + ½ O 2 (g) ½ SO 2 (g) C) 2 S(s) + 5/2 O 2 (g) SO 2 (g) + SO 3 (g) D) SO 3 (g) S(s) + 3/2 O 2 (g) E) 2 S(s) + 3 O 2 (g) 2 SO 3 (g) 15. The reaction that represents the standard enthalpy of formation for glucose (C 6 H 12 O 6 ) is: A) C 6 H 12 O 6 (s) + 6 O 2 6 CO 2 (g) + 6 H 2 O(g) B) 6 C(diamond) + 6 H 2 (g) + 3 O 2 (g) C 6 H 12 O 6 (s) C) 6 C(graphite) + 6 H 2 O(l) C 6 H 12 O 6 (s) D) 6 C(graphite) + 6 H 2 (g) + 3 O 2 (g) C 6 H 12 O 6 (s) E) C 6 H 12 O 6 (s) 6 C(graphite) + 6 H 2 (g) + 3 O 2 (g)
16. Octane (C 8 H 18 ) undergoes combustion according to the following thermochemical equation: 2C 8 H 18 (l) + 25O 2 (g) 16CO 2 (g) + 18H 2 O(l), ΔH rxn = 11,020 kj/mol. Given that ΔH f [CO 2 (g)] = 393.5 kj/mol and ΔH f [H 2 O(l)] = 285.8 kj/mol, calculate the standard enthalpy of formation of octane. A) 210 kj/mol B) 11,230 kj/mol C) 22,040 kj/mol D) 420 kj/mol E) 420 kj/mol 17. Acetylene (C 2 H 2 ) undergoes combustion in excess oxygen to generate gaseous carbon dioxide and water. Given ΔH f [CO 2 (g)] = 393.5 kj/mol, ΔH f [H 2 O(g)] = 241.8 kj/mol, and ΔH f [C 2 H 2 (g)] = 226.6 kj/mol, how much energy is released (kj) when 10.5 moles of acetylene is burned? A) 2,510.8 kj B) 26,400 kj C) 13,200 kj D) 52,700 kj E) 9,050 kj 18. Given Fe 2 O 3 (s) + 3CO(g) 2 Fe(s) + 3 CO 2 (g) ΔH rxn = 24.8 kj, determine the standard enthalpy change for the reaction Fe(s) + 3/2 CO 2 (g) 1/2 Fe 2 O 3 (s) + 3/2 CO(g), A) ΔH = -12.4 kj B) ΔH = +24.8 kj C) ΔH = +12.4 kj D) ΔH = +49.6 kj E) ΔH = 49.6 kj 19. Calculate the standard enthalpy change for the reaction 2C 8 H 18 (l) + 17O 2 (g) 16CO(g) + 18H 2 O(l). Given A) 10.450 kj/mol B) 6,492 kj/mol C) 6,492 kj/mol D) 10,450 kj/mol E) 15,550 kj/mol
20. Given the following ΔH values, H 2 (g) + 1/2 O 2 (g) H 2 O(l) ΔH f = 285.8 kj/mol H 2 O 2 (l) H 2 (g) + O 2 (g) ΔH rxn = 187.6 kj/mol calculate ΔH rxn for the reaction H 2 O 2 (l) H 2 O(l) + 1/2 O 2 (g). A) 98.2 kj/mol B) 88.2 kj/mol C) 78.2 kj/mol D) 68.2 kj/mol E) None of the above 21. Find ΔH rxn for the reaction CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(l). [ΔH f (CH 4 (g)) = 74.8 kj/mol; ΔH f (CO 2 (g)) = 393.5 kj/mol; ΔH f (H 2 O(l)) = 285.5 kj/mol] A) -879.7 kj/mol B) -889.7 kj/mol C) -899.7 kj/mol D) -909.7 kj/mol E) None of the above 22. Select True or False: Chemical reactions in a bomb calorimeter occur at constant pressure. A) True B) False ANSWERS 1. A 2. C 3. A 4. B 5. B 6. C 7. A 8. D 9. E 10. C 11. D 12. A 13. D 14. D 15. D 16. A 17. C 18. C 19. B 20. A 21. B 22. B