Homework #2-solutions

008 100points the vapor pressure of pure acetone ch 3

• Notes
• 7
• 100% (1) 1 out of 1 people found this document helpful

This preview shows page 3 - 5 out of 7 pages.

008 10.0points The vapor pressure of pure acetone (CH 3 COCH 3 ) at 30 o C is 240 torr. If salt (NaCl) is dissolved into a sample of acetone until the total vapor pressure of the mixture at 30 o C is 180 torr, what is the mol fraction of acetone? 1. 0.25 2. 0.75 correct 3. 0.2 4. 0.8 Explanation: P = P o acetone · χ acetone χ acetone = P P o acetone χ acetone = 180 240 = 0 . 75 009 10.0points Which of the following is NOT a colligative property for a solution? 1. depressing the freezing point of the sol- vent 2. osmotic pressure of the solvent 3. molecular weight of the solute correct 4. lowering the vapor pressure of the solvent 5. elevating the boiling point of the solvent Explanation: Colligative properties are properties of so- lutions that depend on the number of solute particles and not the kind of particles. Molec- ular weight depends on the type of particles you have, not how many. 010 10.0points You can tell whether a mixture is a colloid or a solution by 1. stirring it. 2. evaporating off the liquid. 3. letting the mixture stand for a while. 4. shining a light though it. correct Explanation: Light bounces off the colloid’s particles.

Subscribe to view the full document.

clow (twc432) – Homework #2 – holcombe – (51160) 4 011 10.0points What is the molality of carbon tetrachloride in a solution of toluene, if the mole fraction of the carbon tetrachloride is 0.200? The molecular mass of toluene is 92.14 grams per mole. 1. 1.75 m 2. 1.40 m 3. 3.21 m 4. 2.71 m correct 5. 2.34 m Explanation: .2 mol fraction means that .2 mols are CCl 4 and 0.8 mols are toluene (C 6 H 5 CH 3 , 92.14 g/mol). 0.8 mol * 92.14 g/mol = 73.712 g toluene or 0.073712 kg molality = .2 mol / 0.073712 kg = 2.71 m 012 10.0points At 75 , the vapor pressure of water, methanol, diethylether and benzene are 289, 1126, 2680, and 644 torr, respectively. Which of these is NOT above its boiling point at normal atmo- spheric pressure? 1. methanol, diethylether, and benzene 2. water 3. methanol and diethylether 4. water and benzene correct 5. None of these 6. diethylether Explanation: The vapor pressures for water and benzene are still below 760 torr at 75 C, which means that they are not up to the boiling point yet and are in fact, below the boiling point. Methanol and diethylether are well above 760 torr at this temperature which means they are above their normal boiling points. 013 10.0points Each of the following samples was placed in 1 liter of water. I) 0.6 mol NaOH II) 0.7 mol KCl III) 0.5 mol Na 2 CO 3 IV) 1 mol of sugar Rank the solutions that are made in terms of increasing order of boiling point elevation. (Remember your solubility rules.) 1. III, I, II, IV 2. III, I, IV, II 3. IV, II, I, III 4. IV, I, II, III correct 5. II, IV, I, III Explanation: Colligative properties of a solution depend on the number of solute particles in solution, not the type. I) will have 1.2 mol of particles because NaOH completely dissociates in water. II) will have 1.4 mol of particles because KCl completely dissociates in water.
• Fall '07
• Holcombe
• Chemistry, Vapor pressure, Clow

{[ snackBarMessage ]}

What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern