A student collected the following data when measuring the freezing - point of an aqueous solution. What is the freezing - point of the solution? A. 0.5\deg C B. 0.0\deg C C. -0.5\deg C D. - 1.0\deg C E. - 2.0\deg C F. - 3.0\deg C

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?

A 12.0-g sample of a nonelectrolyte is dissolved in 80.0 g of water. The solution freezes at -1.94 C. Calculate the molar mass of the substance.

Arrange the following solutions in order by their decreasing freezing points: 0.1 m Na3PO4, 0.1 m C2H5OH, 0.01 m CO2, 0.151 m NaCI, and 0.21 m cacI2.

The freezing point of a 0.031-m solution of copper(II) sulfate in water is 0.075 C. (a) Calculate the vant Hoff factor, i, for this solution. (b) Would the vant Hoff factor be larger, smaller, or the same for a 0.050-m solution of this compound?

The solubility of NaCl in water at 100 C is 39.1 g/100. g of water Calculate the boiling point of this solution. (Assume i = 1.85 for NaCl.)

Water at 25 C has a density of 0.997 g/cm3. Calculate the molality and molarity of pure water at this temperature.

Concentrated hydrochloric acid contains 1.00 mol HCl dissolved in 3.31 mol H2O. What is the mole fraction of HCl in concentrated hydrochloric acid? What is the molal concentration of HCl?

A solution was prepared by dissolving 0.800 g of sulfur, Sg, in 100.0 g of acetic acid, HC2H3O2. Calculate the freezing point and boiling point of the solution.

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.)