Is water a solvent in this problem?


by lucky_star
Tags: solvent, water
lucky_star
lucky_star is offline
#1
Feb22-09, 09:20 PM
P: 33
The problem statement, all variables and given/known data
Determine the molality of a solution of water dissolved in methanol for which the mole fraction of water is 0.25.

Hi all,
I just want to ask if water in this problem is a solvent or a solute!? Is water always a solvent even though they say "a solution of water dissolved in methanol" in the problem? Please help me clear it up.
Phys.Org News Partner Science news on Phys.org
Review: With Galaxy S5, Samsung proves less can be more
Making graphene in your kitchen
Study casts doubt on climate benefit of biofuels from corn residue
naele
naele is offline
#2
Feb22-09, 09:23 PM
P: 202
It appears you've answered your own question. Also, note the mole fraction of water in the solution.
lucky_star
lucky_star is offline
#3
Feb22-09, 09:57 PM
P: 33
Quote Quote by naele View Post
It appears you've answered your own question. Also, note the mole fraction of water in the solution.
Thanks!!! Yes, and that's how it get me confused. A solvent is what we have more of, and a solute is what we have less. This appears violating the common rule. I think this is an exception right? what do you think?

naele
naele is offline
#4
Feb23-09, 12:53 AM
P: 202

Is water a solvent in this problem?


That's basically how you look at it. Consider a typical aqueous solution, say 1M HCl. That means there's one mole of HCl in one liter of water. But water is at roughly ~55M so there's quite a bit more of it. In this case, we're told that a water/methanol solution has water at 0.25 mole fraction. By extension we know that methanol has to be 1 - 0.25 = 0.75 which of course is greater than 0.25 so we can only conclude that methanol is the solvent here.
lucky_star
lucky_star is offline
#5
Feb23-09, 12:58 AM
P: 33
Yes, that makes sense to me! Thank so much!


Register to reply

Related Discussions
How can water have a molarity if theres no diff b/w solute and solvent? Biology, Chemistry & Other Homework 8
Solvent and UV/V spec Chemistry 4
Choosing a solvent Biology, Chemistry & Other Homework 7
Solvent washing Chemistry 13
how can I solvent collagen? Biology 4