Chapter 11, Problem 49P

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?

Convert the units of Henrys law constant for CO2, in table 7.2, to units of, mmHg, atm, and bar. In which cases does the numerical value of the constant change?

Carbon tetrachloride (CCl4) and benzene (C6H6) form ideal solutions. Consider an equimolar solution of CCl4 and C6H6 at 25C. The vapor above the solution is collected and condensed. Using the following data, determine the composition in mole fraction of the condensed vapor. Substance Gfo C6H6(l) 124.50 kJ/mol C6H6(g) 129.66 kJ/mol CCI4(l) 65.21 kJ/mol CCI4,(g) 60.59 kJ/mol

How do colloids differ from solutions with regard to dispersed particle size and homogeneity?

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.

Maple syrup sap is 3% sugar (sucrose) and 97% water bymass. Maple syrup is produced by heating the sap toevaporate a certain amount of the water. (a) Describe what happens to the composition and boilingpoint of the solution as evaporation takes place. (b) A rule of thumb among maple syrup producers is thatthe finished syrup should boil about 4 C higher than theoriginal sap being boiled. Explain the chemistry behindthis guideline. (c) If the finished product boils 4 C higher than the originalsap, calculate the concentration of sugar in the finalproduct. Assume that sugar is the only solute and theoperation is done at 1 atm pressure.

6-111 As noted in Section 6-8C, the amount of external pressure that must be applied to a more concentrated solution to stop the passage of solvent molecules across a semipermeable membrane is known as the osmotic pressure The osmotic pressure obeys a law similar in form to the ideal gas law (discussed in Section 5-4), where Substituting for pressure and solving for osmotic pressures gives the following equation: RT MRT, where M is the concentration or molarity of the solution. (a) Determine the osmotic pressure at 25°C of a 0.0020 M sucrose (C12H22O11) solution. (b) Seawater contains 3.4 g of salts for every liter of solution. Assuming the solute consists entirely of NaCl (and complete dissociation of the NaCI salt), calculate the osmotic pressure of seawater at 25°C. (c) The average osmotic pressure of blood is 7.7 atm at 25°C. What concentration of glucose (C6H12O6) will be isotonic with blood? (d) Lysozyme is an enzyme that breaks bacterial cell walls. A solution containing 0.150 g of this enzyme in 210. mL of solution has an osmotic pressure of 0.953 torr at 25°C. What is the molar mass of lysozyme? (e) The osmotic pressure of an aqueous solution of a certain protein was measured in order to determine the protein's molar mass. The solution contained 3.50 mg of protein dissolved in sufficient water to form 5.00 mL of solution. The osmotic pressure of the solution at 25°C was found to be 1.54 torr. Calculate the molar mass of the protein.

Define the normal boiling point of water. Why does a sample of boiling water remain at the same temperature until all the water has been boiled? Define the normal freezing point of water. Sketch a representation of a heating/cooling curve for water, marking clearly the normal freezing and boiling points.

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?