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Material Type: Exam; Class: Gen Chem-Sci; Subject: Chemistry; University: University of Massachusetts - Amherst; Term: Spring 2009;
Typology: Exams
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Chemistry 112, Spring 2008 , Section 1& 3 (Hardy) Exam 1 (100 points) 18 Feb 2009 YOU MUST: Put your name and student ID on the bubble sheet correctly. Put the exam version ID on the bubble sheet. The exam number is found on the subsequent pages e.g. ID:A, ID:B, ID:C etc. Put all your answers on the bubble sheet.
Name: ______________________ Class: _________________ Date: _________ ID: D
Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. What mass of Na 2 SO 4 must be dissolved in 75.0 grams of water to lower the freezing point by 2.50 °C? The freezing point depression constant, K fp, of water is –1.86 °C/ m. Assume the van't Hoff factor for Na 2 SO 4 is 2.40. a. 23.3 g b. 44.0 g c. 0.310 g d. 5.97 g e. 3.30 g ____ 2. Which of the following phase transitions is/are exothermic?
Name: ______________________ ID: D ____ 10. The heat of formation of NaCl(s) is –411.1 kJ/mol and the heat of formation of NaCl(aq, 1 m ) is –407. kJ/mol. Determine the heat of solution of NaCl. Will the solution temperature increase or decrease when NaCl is dissolved in water? a. –818.4 kJ/mol; decrease b. –3.8 kJ/mol; increase c. +3.8 kJ/mol; decrease d. +818.4 kJ/mol; increase e. +3.8 kJ/mol; increase ____ 11. Which one of the following molecules will exhibit dipole-dipole intermolecular forces as a pure liquid? a. CO 2 b. C 2 H 2 c. SO 3 d. NO 2 e. F 2 ____ 12. If 355 g of ethanol (C 2 H 5 OH) is added to 645 g of water, what is the molality of the ethanol? a. 55.0 m b. 7.71 m c. 21.7 m d. 11.9 m e. 0.550 m ____ 13. If 18.4 g KCl is dissolved in 2.50 × 102 g H 2 O, what is the weight percent of KCl in the solution? a. 97.2% b. 7.36% c. 6.86% d. 7.94% e. 0.972% ____ 14. Which of the following are valid reasons why vegetable oil has a greater viscosity than diethyl ether, CH 3 OCH 3?
Name: ______________________ ID: D ____ 16. The osmotic pressure of blood is 7.65 atm at 37 °C. What mass of glucose (C 6 H1 2O 6 , molar mass = 180. g/mol) is needed to prepare 2.25 L of solution for intravenous injection? The osmotic pressure of the glucose solution must equal the osmotic pressure of blood. ( R = 0.08206 L⋅atm/mol⋅K) a. 1.02 × 103 g b. 5.67 g c. 122 g d. 0.698 g e. 0.676 g ____ 17. At its boiling point of –34.0 °C, 6.33 kJ of heat is required to vaporize 22.0 g of chlorine (Cl 2 ). What is the molar enthalpy of vaporization of chlorine? a. 0.286 kJ/mol b. 20.4 kJ/mol c. 0.0893 kJ/mol d. 139 kJ/mol e. 1.96 kJ/mol ____ 18. The Henry's law constant for N 2 in water at 37 °C is 8.2 × 10 – 7^ M/mm Hg. What is the equilibrium concentration of N 2 in water when the partial pressure of N 2 is 605 mm Hg? a. 2.0 × 103 M b. 5.0 × 10 – 4^ M c. 6.5 × 10 – 7^ M d. 7.4 × 108 M e. 1.4 × 10 – 9^ M ____ 19. If 3.01 g of water is sealed in an evacuated 2.00 L flask and heated to the normal boiling point of 373 K, what is the pressure in the flask? ( R = 0.08206 L⋅atm/mol⋅K) a. 2.56 atm b. 1.00 atm c. 0.678 atm d. 0.391 atm e. 46.1 atm ____ 20. Mount Everest rises to a height of 8.850 × 103 m above sea level. At this height, the atmospheric pressure is 231 mm Hg. At what temperature (in °C) does water boil at the summit of Mount Everest? The vapor pressure of water at 373 K is 760.0 mm Hg. (Δvap H ° for H 2 O = 40.7 kJ/mole and R = 8. J/K⋅mol) a. 72 °C b. 69.0 °C c. 4.07 °C d. 87 °C e. 364 °C