Vapor Pressure / pressure

I need an explanation for this Chemistry question to help me study.

Question 1:

The freezing point of an aqueous solution(solute is not an electrolyte) is -2.79C.

Calculate the vapor pressure at 25C. Vapor pressure of pure water at 25C is 23.76 torr and the freezing point depression constant of water is 1.86 C kg / mol

Question 2:

path traveled is at least 1 meter. Collisions randomize the motion of the molecular ions and prevent them from reaching the detector. Assuming the molecular ion of H2 O has a collision cross section of 1.00 nm^2, calculate the appropriate pressure for the detector region of a mass spectrometer. Assume T=298K