Question #66c6e
1 Answer
The vapor pressure of the solution will be 115 torr.
You're dealing with a solution that consists of a non-volatile solute, sodium chloride, and water, which will be your solvent.
The general idea is that the vapor pressure of a solution that contains a non-volatile solute will be lower than the vapor pressure of th pure solvent, under the same conditions.
This is known as Raoult' Law, which is mathematically expressed as
Since you know that the vapor pressure of pure water at
To do that, you need the value of its density at that temperature, which you can find here:
http://antoine.frostburg.edu/chem/senese/javascript/water-density.html
So, use water's volume and density to calculate its mass
Use the molar masses of water and sodium chloride to determine how many moles of each you have
and
The total number of moles present in the solution will be
The mole fraction of water will be
The vapor pressure of the solution will thus be
Rounded to three sig figs, the answer will be