Exam 1A 2006

Exam 1A 2006 - Name _ Key A Exam I July 20, 2006 200 points...

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Name ____________________________________________ Key A Exam I July 20, 2006 200 points Each question is worth 5 points. Part A. Multiple Choice. Please clearly circle the ONE correct answer for each question. 1. All of the following are network covalent solids except: a. diamond b. graphite c. iron d. quartz e. silicon carbide Consider the following phase diagram from questions 2 and 3: 2. A change from point X to point Y corresponds to a. evaporation b. melting c. freezing d. sublimation e. condensation 3. The point corresponding to the critical point is a. A b. B c. C d. D e. E Pressure B A C D X Y
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CHEM102_Su06 Exam I 2 4. A 12.0% (w/w) sucrose solution has a density of 1.05 g/mL. The number that gives the best value for the mass of sugar in 55 mL of this solution is a. 6.6 g b. 6.60 g c. 6.93 g d. 58 g e. 6.9 g 5. An ideal solution is formed from a mixture of the nonvolatile solute urea, CO(NH 2 ) 2 (molar mass = 60.0 g/mol), and methanol, CH 3 OH (molar mass = 32.0 g/mol). The vapor pressure of pure methanol at 20 °C is 89 mmHg. Calculate the mole fraction of urea that is obtained from mixing 6.0 g of urea with 32.0 g of methanol. a. 0.16 b. 0.10 c. 0.091 d. 0.91 e. 0.84 6. Calculate the vapor pressure of the methanol solution described in question 5. a. 8.1 mmHg b. 81 mmHg c. 8.9 mmHg d. 75 mmHg e. 14 mmHg 7. Pure glacial acetic acid, HC 2 H 3 O 2 , has a molar mass of 60.05 g/mol, a density of 1.049 g/mL, a freezing point of 16.62 °C, and a boiling point of 118.3°C. Its freezing point and boiling point elevation constants are: K f = 3.57 °C/ m ; K b = 3.07 °C/ m . A solution was made by dissolving 19.51 g of an unknown molecular solid into 181.0 g of glacial acetic acid. The measured boiling point of the solution was 125.16 °C. Calculate the molar mass of the unknown substance. a. 24.4 g/mol b. 30.5 g/mol c. 45.3 g/mol d. 48.2 g/mol e. 174 g/mol 8. Which of the following is expected to have the greatest surface tension? a.
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Exam 1A 2006 - Name _ Key A Exam I July 20, 2006 200 points...

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