First problem:

As a scuba diver descends under water, the pressure increases. At a total air pressure of 2.58 atm and a temperature of 25.0 C, what is the solubility of N2 in a diver's blood? [Use the value of the Henry's law constant k calculated in Part A, 6.26 * 10^-4 mol/Latm

Assume that the composition of the air in the tank is the same as on land and that all of the dissolved nitrogen remains in the blood.

I am having trouble figuring out the partial pressure. Any help?

part A had a partial pressure of .78atm. THis is part a:

Air is a mixture of gases that is about 78.0% N2 by volume. When air is at standard pressure and 25.0 C, the N2 component will dissolve in water with a solubility of 4.88* 10^-4 M. What is the value of Henry's law constant for N2 under these conditions?

Second problem:

At what temperature would a 2.00 m NaCl solution freeze, given that the van't Hoff factor for NaCl is 1.9? Kf for water is 1.86 C/m.

I am just lost as to how to approach this.

Thanks,

Brent