The vapor pressure of ethanol is 54.68 mm Hg at 25°C. How many grams of testosterone, C19H28O2, a nonvolatile, nonelectrolyte (MW = 288.4 g/mol), must be added to 267.4 grams of ethanol to reduce the vapor pressure to 53.77 mm Hg ? ethanol = CH3CH2OH = 46.07 g/mol.  ??g testosterone

Pure ethylene glycol, HOCH2CH2OH, is added 2.00 kg of water in the cooling system of a car. The vapor pressure of the water in the system when the temperature is 90 C is 457 mm Hg. What mass of glycol was added? (Assume the solution is ideal. See Appendix G for the vapor pressure of water.)

A forensic chemist is given a white solid that is suspected of being pure cocaine (C17H21NO4, molar mass = 303.35 g/mol). She dissolves 1.22 0.01 g of the solid in 15.60 0.01 g benzene. The freezing point is lowered by 1.32 0.04C. a. What is the molar mass of the substance? Assuming that the percent uncertainty in the calculated molar mass is the same as the percent uncertainty in the temperature change, calculate the uncertainty in the molar mass. b. Could the chemist unequivocally state that the substance is cocaine? For example, is the uncertainty small enough to distinguish cocaine from codeine (C18H21NO3, molar mass = 299.36 g/mol)? c. Assuming that the absolute uncertainties in the measurements of temperature and mass remain unchanged, how could the chemist improve the precision of her results?

An aqueous solution containing 10.0 g of starch per liter has an osmotic pressure of 3.8 mm Hg at 25 C. (a) What is the average molar mass of starch? (The result is an average because not all starch molecules are identical.) (b) What is the freezing point of the solution? Would it be easy to determine the molecular weight of starch by measuring the freezing point depression? (Assume that the molarity and molality are the same for this solution.)

What is the freezing point and normal boiling point of a solution made by adding 39 mL of acetone, C3H6O, to 225 mL of water? The densities of acetone and water are 0.790 g/cm3 and 1.00 g/cm3, respectively.

Insulin is a hormone responsible for the regulation of glucose levels in the blood. An aqueous solution of insulin has an osmotic pressure of 2.5 mm Hg at 25C. It is prepared by dissolving 0.100 g of insulin in enough water to make 125 mL of solution. What is the molar mass of insulin?

Two samples of sodium chloride solutions are brought to a boil on a stove. One of the solutions boils at 100.10C and the other at 100.15C. a Which of the solutions is more concentrated? b Which of the solutions would have a lower freezing point? c If you split the solution that boils at 100.1C into two portions, how would the boiling points of the samples compare? Which of the following statements do you agree with regarding the determination of your answer for part c? I. The question cannot be answered with certainty without knowing the volumes of each portion. II. Making the necessary assumption that the two samples have equal volumes, I was able to correctly answer the question. III. The volumes that the sample was split into are irrelevant when determining the correct answer.

Consider two hypothetical pure substances, AB(s) and XY(s). When equal molar amounts of these substances are placed in separate 500-mL samples of water, they undergo the following reactions: AB(s)A+(aq)+B(aq)XY(s)XY(aq) a Which solution would you expect to have the lower boiling point? Why? b Would you expect the vapor pressures of the two solutions to be equal? If not, which one would you expect to have the higher vapor pressure? c Describe a procedure that would make the two solutions have the same boiling point. d If you took 250 mL of the AB(aq) solution prepared above, would it have the same boiling point as the original solution? Be sure to explain your answer. e The container of XY(aq) is left out on the bench top for several days, which allows some of the water to evaporate from the solution. How would the melting point of this solution compare to the melting point of the original solution?

Will red blood cells crenate, hemolyze, or remain unaffected when placed in each of the solutions in Problem 8-102?

Sodium chloride (NaCl) is commonly used to melt ice on roads during the winter. Calcium chloride (CaCl2) is sometimes used for this purpose too. Let us compare the effectiveness of equal masses of these two compounds in lowering the freezing point of water, by calculating the freezing point depression of solutions containing 200. g of each salt in 1.00 kg of water. (An advantage of CaCl2 is that it acts more quickly because it is hygroscopic, that is. it absorbs moisture from the air to give a solution and begin the process. A disadvantage is that this compound is more costly.)