Explanation 020 part 1 of 1 10 points The vapor pressure of water at 37 C is

Explanation 020 part 1 of 1 10 points the vapor

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Explanation: 020 (part 1 of 1) 10 points The vapor pressure of water at 37 C is 47.1 torr and its enthalpy of vaporization is 44.0 kJ · mol - 1 . Estimate the vapor pressure of wa- ter at 87 C. Assume the enthalpy of vaporiza- tion of water is independent of temperature. 1. 713 torr 2. 504 torr correct 3. 112 torr 4. 256 torr 5. 52 torr Explanation: 021 (part 1 of 1) 10 points Consider the temperature composition dia- gram of a binary mixture of A and B which forms a minimum boiling azeotrope: Initially X A = 0 . 6. 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 0 20 40 60 80 100 120 140 X A boiling temperature ( C) Which of the following is true if the distil- late is collected from a distillation apparatus while the solution boils? 1. X A in the beaker will remain the same. 2. X A in the beaker will approach 0. 3. X A in the beaker will approach 1. 4. X A in the beaker will approach 0.3. cor- rect Explanation: 022 (part 1 of 1) 10 points Mixing 17.6 kg of ethylene glycol (commercial antifreeze, C 2 H 6 O 2 ) with 6.00 gal of water lowers the freezing point to - 10 . 0 F. Suppose you wanted to accomplish the same thing with sugar (sucrose, C 12 H 22 O 11 ) instead of ethy- lene glycol. How many kilograms of sucrose would you use? 1 gallon = 3.785 liters. K f for water = 1 . 86 C/m. 1. 3.09 kg 2. 97.1 kg correct
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Thompson, Margaret – Exam 1 – Due: Sep 18 2007, 3:00 pm – Inst: James Holcombe 8 3. 4 . 68 × 10 - 3 kg 4. 17.6 kg 5. 6019 kg Explanation: 023 (part 1 of 1) 10 points Several interesting observations from the world around you are listed below. Which of these is NOT explained by a colligative property? 1. Water boils at a higher temperature when salt is added. 2. Antifreeze is added to a car radiator to keep the car from overheating. 3. The freezing point of water is lowered when salt is added. 4. A lobster will die when placed in fresh water. 5. At high altitude it takes longer to cook spaghetti. correct Explanation: Colligative properties of a solution depend on the number of solute particles in solution, not the type. Boiling point variations due to pressure changes have nothing to do with solutions and colligative properties (boiling point variations due to particles in solution, etc.). 024 (part 1 of 3) 10 points Consider the following pressure diagram for a binary liquid containing A and B. 0 1 x A 70 torr 20 torr If 8 mol of A and 8 mol of B are mixed, what is the vapor pressure of B? 1. 20 torr 2. 35 torr correct 3. 45 torr 4. 10 torr 5. 70 torr Explanation: The mole fraction of A is x A = mol A total mol = 8 mol 8 mol + 8 mol = 0 . 5 . 0 1 0 . 5 20 torr 35 torr 025 (part 2 of 3) 10 points What is the corresponding vapor pressure of A? 1. 35 torr 2. 10 torr correct 3. 20 torr 4. 45 torr
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Thompson, Margaret – Exam 1 – Due: Sep 18 2007, 3:00 pm – Inst: James Holcombe 9 5. 70 torr Explanation: 0 1 0 . 5 20 torr 10 torr 026 (part 3 of 3) 10 points What is the corresponding total vapor pres- sure? 1. 20 torr 2. 35 torr 3. 45 torr correct 4. 70 torr 5. 10 torr Explanation: 0 1 0 . 5 20 torr 45 torr 027 (part 1 of 1) 10 points Arrange H 2 O, NH 3 , Ar, and NaCl in order of expected increasing boiling points.
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