4 Part A MISSED THIS? Watch KCV: Colligative Properties IWE: Freezing Point Depression; Read Section 13.6. You can click on the Review link to access the section in your eText. An aqueous solution containing 36.7 g of an unknown molecular (non-electrolyte) compound in 152.4 g of water was found to have a freezing point of-1.4 °C. Calculate the molar mass of the unknown compound. Express your answer using two significant figures. ΑΣΦ M= Submit Request Answer Provide Feedba ? g/mol Nex

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.)

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?