A solution of salt dissolved in water is diluted with additional water.....?

Question

A solution of salt dissolved in water is diluted with additional water. Indicate whether the dilution process will cause the value of V to:

decrease

increase

stay the same

Thanks

Answer 1

If you have a certain volume of solution and you add more water to it, the volume of the solution must increase.

Answer 2

If V=volume of salt, it will stay the same.

If V=volume of solution, it will increase.

Answer 3

In that case it seems like a silly question.  It should be self-evident that adding more solvent will increase the volume of the solution.

What else will change?  The concentration of the salt will decrease with additional water.  

Perhaps the V is actually a gamma, which represents the activity coefficient.  A gamma could look like a V.  I'm willing to bet it is.  As a solution becomes more dilute the activity coefficient increases toward 1.  In concentrated solutions the activity coefficient is less than one.  That means that your effective concentration, or the concentration of the ions in solution, will be less than the concentration.  This reduction is due to "ion pairing".

As the solution becomes more dilute, there is less ion pairing and the actual concentration of the ions gets close to the calculated concentration.  The actual concentration of the ions, so to speak, is the activity.

And the activity coefficient, gamma, is the value that we multiply the concentration by in order to get the activity.

So back to your question.  As the solution become more dilute the activity coefficient increases.

=====  Reply to Sarah =====

It's only silly if the variable is volume, but I'm willing to bet your life that it's the activity coefficient, and what you thought was a V is actually gamma.