Question

1) Use Henry's law to determine the molar solubility of helium at a pressure of 1.9 atm and 25 ∘C. Henry’s law constant for helium gas in water at 25 ∘C is 3.70⋅10−4M/atm.

2) A 2.800×10⁻²M solution of NaCl in water is at 20.0∘C. The sample was created by dissolving a sample of NaCl in water and then bringing the volume up to 1.000 L. It was determined that the volume of water needed to do this was 999.2 mL . The density of water at 20.0∘C is 0.9982 g/mL.

Calculate the molality of the salt solution.

Calculate the mole fraction of salt in this solution.

Calculate the concentration of the salt solution in percent by mass.

3)How much dry solute would you take to prepare each of the following solutions from the dry solute and the solvent?

b)120 g of 0.200 m NaNO3

c)120 g of 1.4 % NaNO3 solution by mass

d) How much solvent would you take to prepare the solution in part B?

e)How much solvent would you take to prepare the solution in part C?

4) The Safe Drinking Water Act (SDWA) sets a limit for mercury-a toxin to the central nervous system-at 0.002

ppm by mass. Water suppliers must periodically test their water to ensure that mercury levels do not exceed this limit. Suppose water becomes contaminated with mercury at twice the legal limit (0.004 ppm).

How much of this water would have to be consumed for someone to ingest 50 mg of mercury?

5)A solution contains a mixture of pentane and hexane at room temperature. The solution has a vapor pressure of 252

torr . Pure pentane and hexane have vapor pressures of 425 torr and 151 torr, respectively, at room temperature.

What is the mole fraction of hexane? (Assume ideal behavior.)

Answer 1