Homework Solutions

January 29

16:72    a.    condensation:  gas goes to liquid
            b.    evaporation:  liquid goes to gas
            c.    sublimation:  solid goes to gas
            d.    supercooled liquid:  when a substance is a liquid below its freezing point.

17:39    P = k*c;   k = P/c = 0.791 atm/8.21 x 10^-4 mol/L = 962.2 atm L/mole

If P = 1.10 atm, c = P/k = 1.14 x 10^-3 mol/L

17:42  50.0 g glucose/180.16 g/mole = 0.278 mole glucose

600.0 g water/18.016 g/mole = 33.304 mole water

P(soln) = x(water)*P(pure water)                P(pure water) = 23.8 torr            x(water) = n(water)/n(water) + n(glucose) = 0.9917

P(soln) = 0.9917*23.8 torr = 23.6 torr

17:54    4.9 g sucrose / 342.296 g/mole = 0.014315 mole sucrose

175 g water = 0.175 kg water

m = 0.014315 mole glucose/0.175 kg water = 0.08077 m

K(b)(water) = 0.51 deg kg/mol                                K(f)(water) = 1.86 deg kg/mol

DT_b =(0.51 deg kg/mol)*(0.08077 mol/kg) = 0.0412 deg                Tb = 100.0412 deg = 100.0 deg C

DT_f = (1.86 deg kg/mol)*(0.08077 mol/kg) = 0.150 deg                    Tf = -0.150 deg C