2. kH, the Henry’s Law constant, for oxygen (O2) in water is 1.71 x 10-6 mol/L torr at 298°K. Furthermore, we know that air at sea level (1 atm.) is 21% oxygen. a. Under standard conditions (298 °

CHM/151 Week 1 Problem Set – Rev. 1

Complete the following problems. Submit the solutions showing all work, step-by-step (when

appropriate) as either an MS Word document or handwritten and scanned as a PDF document.

1. At 25 °C, exactly 29.9 g of barium bromide (BaBr2) will dissolve in 100 g of formamide

(CH3NO), an organic solvent.

a. Calculate the percent mass of both formamide and barium bromide in this

solution.

b. Calculate the molality of a saturated solution of barium bromide in formamide.

2. kH, the Henry’s Law constant, for oxygen (O2) in water is 1.71 x 10-6 mol/L torr at 298°K.

Furthermore, we know that air at sea level (1 atm.) is 21% oxygen.

a. Under standard conditions (298 °K and 760 torr total pressure) calculate the

solubility (moles/liter) of O2 in water.

b. Calculate the mass of O2 in grams dissolved in a fishing pond whose volume is 5

x 107 liters when the temperature is 298°K and atmospheric pressure of air is 1

atm.

3. The halogen bromine (Br2) is a liquid at room temperature (25 °C) and somewhat

soluble in water. A saturated solution of Br2 contains 3.3 x 10-4 g Br2 dissolved in 1 g H2O

at room temperature. On the other hand bromine is somewhat more soluble in very

cold water. A saturated solution of Br2 in water at 0 °C contains 4.2 x 10-4 g Br2 in 1 g

H2O. Calculate the mole fraction of bromine in water in both solutions. Calculate the

molality of bromine in both solutions presuming that the density of water is 1 g/cm3.

4. The freezing point depression constant for water is 1.86 °C/m. An aqueous solution of

magnesium chloride (MgCl2) is found to have a freezing point of -2.31 °C. Calculate the

molality of MgCl2 in this solution.

5. Consider the following reaction occurring in water: