vapor pressure calculation help

[Smooth Operater]

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58 grams of NaCl are added to 1 liter of pure water. The soln is heated to 100 Celsius. What is the vapor pressure?

The answer is 747 torr, but I am not sure how to carry out such calculation. I just kinda elimiate all the other choices on my multiple choice.

thank!

 

[Gordon9721]

i think i have a handle on this one, but i'd like to know what the other options were.
i'm not sure if there is a calculation that you really need to use. i'm thinking that since the vapor pressure of pure water is 760 torr, and since you're adding some solute to the solvent, you're making it impure. similar to adding salt to water to make it boil quicker-adding salt to water will lower the vapor pressure? does that make any sense? so since 747 is slightly lower than 760, that was probably the best answer, assuming there were some outrageous numbers as options. anyways, hope that helps, check out raoult's law for more info.

say a prayer for me, taking DAT sept 30.

 

[doc toothache]

The problem can be solved by using Raoult's Law. The expression is:

Partial pressure of water= vapor pressure of pure water x mole fraction of water in the solution.

58 g NaCl=1 mole 1 L water=1000g=55.55 moles water

mole fraction water= 55.55/56.55= 0.9823

pp of water=760(0.9823)=746.56