Given: Mass of lauric acid (g): 8.000g Mass of benzoic acid (g): 1.027g Freezing temperature of pure lactic acid(°C): 43.3°C Freezing point of the benzoic acid-lauric acid mixture(°C): 39.8°C   Question: Calculate molality (m,) in mol/kg, using the formula ΔTf = m × Kf. The Kf value for lauric acid is 3.9°C x kg/mol.

a. Use the following data to calculate the enthalpy of hydration for calcium chloride and calcium iodide. Lattice Energy Hsoln CaCl2(s) 2247kj/mol 46kj/mol Cal2(s) 2059kj/mol 104kj/mol b. Based on your answers to part a, which ion, Cl or I, is more strongly attracted to water?

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.

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?

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.)

You have read that adding a solute to a solvent can both increase the boiling point and decrease the freezing point. A friend of yours explains it to you like this: The solute and solvent can be like salt in water. The salt gets in the way of freezing in that it blocks the water molecules from joining together. The salt acts like a strong bond holding the water molecules together so that it is harder to boil. What do you say to your friend?

For each of the following pairs of solutions, select the solution for which solute solubility is greatest. a. Oxygen gas in water with P = 1 atm and T = 10C Oxygen gas in water with P = 1 atm and T = 20C b. Nitrogen gas in water with P = 2 atm and T = 50C Nitrogen gas in water with P = 1 atm and T = 70C c. Table salt in water with P = 1 atm and T = 40C Table salt in water with P = 1 atm and T = 70C d. Table sugar in water with P = 3 atm and T = 30C Table sugar in water with P = 1 atm and T = 80C

Using KF as an example, write equations that refer to Hsoln and Hhyd Lattice energy was defined in Chapter 3 as H for the reaction K+(g) + F (g) KF(s). Show how you would utilize Hesss law to calculate Hso1n from Hhyd and HLE for KF, where HLE = lattice energy. Hsoln for KF, as for other soluble ionic compounds, is a relatively small number. How can this be since Hhyd and HLE are relatively large negative numbers?

For each of the following pairs of solutions, select the solution for which solute solubility is greatest. a. Ammonia gas in water with P = 1 atm and T = 50C Ammonia gas in water with P = 1 atm and T = 90C b. Carbon dioxide gas in water with P = 2 atm and T = 50C Carbon dioxide gas in water with P = 1 atm and T = 50C c. Table salt in water with P = 1 atm and T = 60C Table salt in water with P = 1 atm and T = 50C d. Table sugar in water with P = 2 atm and T = 40C Table sugar in water with P = 1 atm and T = 70C

Consider three test tubes. Tube A has pure water. Tube B has an aqueous 1.0 m solution of ethanol, C2H5OH. Tube C has an aqueous 1.0 m solution of NaCl. Which of the following statements are true? (Assume that for these solutions 1.0m=1.0M.) (a) The vapor pressure of the solvent over tube A is greater than the solvent pressure over tube B. (b) The freezing point of the solution in tube B is higher than the freezing point of the solution in tube A. (c) The freezing point of the solution in tube B is higher than the freezing point of the solution in tube C. (d) The boiling point of the solution in tube B is higher than the boiling point of the solution in tube C. (e) The osmotic pressure of the solution in tube B is greater than the osmotic pressure of the solution in tube C.