Chemistry B-Colligative Properties-Assignment/Quiz

Determine the freezing point of a 0.51 molal solution of benzoic acid in chloroform. Chloroform has a freezing point of -63.5°C and a freezing point depression constant of 4.70°C•kg/mol. What is the freezing point of this solution?

-65.9

A set of four 15.0-mL solutions—each in a similar open dish—was left at room temperature, and the amount that remained was recorded after every hour. Which of the solutions do you expect to be the first to completely evaporate from the open dish?

0.25 m Na2SO4

Determine the boiling point of a solution made by dissolving 0.60 mol K2SO4 in 1.0 kg water. Water has a boiling point elevation constant of 0.51°C•kg/mol. What is the boiling point of this solution?

100.92

A solution contains 6.21 g of ethylene glycol dissolved in 25.0 g of water. If water has a boiling point elevation constant of 0.512°C•kg/mol, what is the boiling point of the solution? (molar mass of ethylene glycol = 62.1 g/mol; boiling point of pure water = 100.00°C)

102.05°C

A group of students in a school laboratory want to identify an unknown substance by investigating its effect on the boiling point of carbon tetrachloride. They added 9.15 g of the unknown substance to 515 g of carbon tetrachloride, and they observed a boiling point elevation of 0.49°C. If carbon tetrachloride has a boiling point elevation constant of 4.95°C•kg/mol, what is the molar mass of the unknown substance?

180 g/mol

0.5 mol NaCl 1.0 mol K3PO4 2.0 mol glucose 1.5 mol ethylene glycol 0.8 mol MgCl2

5,1,3,4,2

What mass of solid that has a molar mass 89.0 g/mol should be added to 100.0 g of benzene to raise the boiling point of benzene by 2.42°C? (The boiling point elevation constant of benzene is 2.53°C•kg/mol.)

8.52 g

When 4.88 g of toluene is dissolved in 50.0 g of liquid benzene, the freezing point of the liquid is 0.06°C. If the normal freezing point for benzene is 5.50°C and its freezing point depression constant is 5.12°C•kg/mol, what is the molar mass of toluene?

92.0 g/mol

Which graph correctly shows the effect on the freezing point caused by increasing the molality of a solution ?

A mc004-1.jpg

A group of students is in the laboratory performing an experiment on the effect of adding salt to water. Which observation are students likely to make as they increase the molality of the saltwater solution?

As the molality increases by 1 m, there is a corresponding decrease of 1.86°C in the solution's freezing point.

Students were investigating the effects of electrolytes and nonelectrolytes on water. A number of experiments using equal concentrations of sodium chloride and glucose showed that sodium chloride in water had a greater change on the water's freezing point. What is the reason behind this observation?

B

What is the relationship between the concentration of particles in a solution and the solution's vapor pressure?

B

Which of the following is a nonelectrolyte?

C6H12O6

Which points did you include in your response? Check any that apply.

Check All

Which of the following substances will cause the greatest temperature change if the same amount of each substance is added to 1.0 kg of water?

D

When an accident victim who has lost blood is admitted to a hospital, saline is usually administered to maintain blood osmotic pressure. Saline is a solution that contains a certain amount of NaCl and is designed to have the same osmotic pressure as normal blood cells. Which of the following explains why glucose of the same molality cannot attain the same effect as saline?

Each formula unit of NaCl will give two particles because of ionization, but each molecule of glucose dissolves to give only one particle. Osmotic pressure for glucose will be lower than is required.

Which statement about electrolytes and nonelectrolytes is not true?

Electrolytes disperse as molecules in a solution.

A student placed honey in an open dish and an equal volume of water in a second open dish and left them at room temperature for 8 hours. After examining the containers, the student realized that the amount of water had decreased, but the amount of honey seemed unchanged. Which statement correctly explains this phenomenon?

Honey is a highly concentrated solution of sugar in water and has a much lower vapor pressure than pure water has. So, pure water evaporates at a much higher rate.

Consider two solutions made using water as the solvent: 1.0 m CaCl2 and 3.0 m sucrose. Describe how the osmotic pressures of these two solutions compare. Explain why this is true.

The osmotic pressure of the two solutions are the same

A group of students in the laboratory are studying the effects of solutes on solvents. They are comparing water and a solution of sodium chloride. Which statement correctly describes the expected results of this experiment?

The salt solution will have a higher boiling point, a lower freezing point, and a lower vapor pressure.

Antifreeze protects cars from freezing and overheating. A student wants to identify an antifreeze that will save the family car's cooling system from freezing during winter when the temperatures are expected to reach -6.0°C. One of the brands is prepared by mixing 60.0 g of ethylene glycol, the antifreeze, in 250 g of water. Calculate the freezing point of the antifreeze. Will this antifreeze be helpful in protecting the car? The freezing point depression constant for water is 1.86°C•kg/mol, and the molar mass of ethylene glycol is 62.0 g/mol.

freezing point = -7.2°C; helpful

Which of the following best explains freezing point depression?

the decrease in the freezing point of a solution as a function of the number of particles that are dissolved in the solution

The osmotic pressure of a solution increases as

the number of particles of solute in the solution increases.

Which of the following does not involve colligative properties?

Not A

A student lives in a place that receives lots of snow and ice during the winter. The student has observed that the highway department spreads salt on the road after a snowfall. Which of the following correctly explains why the highway department uses salt on the roads?

Salt lowers the freezing point of water, which makes the melted snow on the road less likely to form ice.

Which statement explains why an increase in molality increases the boiling point of a solution?

The addition of solute decreases the solvent's vapor pressure. A higher temperature must then be applied to overcome the change.