91Ó°ÊÓ

Calculate the freezing point depression of mercury caused by dissolved sodium if the mole fraction of \(\mathrm{Na}\) is \(0.0477\). The normal freezing point of \(\mathrm{Hg}\) is \(-39^{\circ} \mathrm{C}\) and its enthalpy of fusion is \(2331 \mathrm{~J} / \mathrm{mol}\).

Calculate the cryoscopic and ebullioscopic constants for liquid bromine, \(\mathrm{Br}_{2}\). You will need the following data: $$ \begin{array}{ll} \Delta_{\text {fus }} H: 10.57 \mathrm{~kJ} / \mathrm{mol} & \text { MP: }-7.2^{\circ} \mathrm{C} \\ \Delta_{\text {vap }} H: 29.56 \mathrm{~kJ} / \mathrm{mol} & \text { BP: } 58.78^{\circ} \mathrm{C} \end{array} $$

Which constant is usually larger for a solvent, the cryoscopic constant or the ebullioscopic constant? Why?

A 200,000 -amu average molecular weight polymer is contaminated with \(0.5 \%\) of a 100 -amu impurity, presumably the monomer. Determine the error in the molecular weight determination if a \(1.000 \times 10^{-4}\) molal aqueous solution is used. Assume a temperature of \(25.0^{\circ} \mathrm{C}\).

Consider an aqueous solution of a polymer that has an average molecular weight of 185,000 amu. Calculate the molality that is needed to exert an osmotic pressure of \(30 \mathrm{~Pa}\) at \(37^{\circ} \mathrm{C}\). How many grams per kilogram of solvent is this?

Determine osmotic pressures for each solution given. Assume complete dissociation of the solute. (a) \(10.0 \mathrm{~g}\) of \(\mathrm{KBr}\) in \(100.0 \mathrm{~g} \mathrm{H}_{2} \mathrm{O}\) at \(20.0^{\circ} \mathrm{C}\) (b) \(20.0 \mathrm{~g}\) of \(\mathrm{SrCl}_{2}\) in \(100.0 \mathrm{~g} \mathrm{H}_{2} \mathrm{O}\) at \(80.0^{\circ} \mathrm{C}\) (c) \(0.100\) molal \(\mathrm{HCl}\) at \(37.0^{\circ} \mathrm{C}\) (This is a good approximation of stomach acid.)