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Topic: Help in calculating melting point  (Read 6225 times)

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Offline meghan

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Help in calculating melting point
« on: February 27, 2010, 08:45:27 AM »
I'm not sure what the final step would be in the problem below.  I have solved for  :delta:T for freezing and boiling points already.

Q: Calculate the melting point of a 1.7 m solution of sodium chloride assuming 100% dissociation.  For water kbp=0.512 degree C/m and kfp = 1.86 degree C/m.

I don't know how to get melting point.  Is the difference between the change in freezing point and melting point?  Here's what I did so far.

 :delta:Tbp =kbpmsol particles
 :delta:Tbp = .512 C/m x 1.70 m
 :delta:Tbp = .870 C

 :delta:Tfp =kfpmsol particles
:delta:Tfp = .1.86 C/m x 1.70 m
:delta:Tfp = 3.16 C

Thanks for your help. 

Offline Schrödinger

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Re: Help in calculating melting point
« Reply #1 on: February 27, 2010, 01:10:39 PM »
Q: Calculate the melting point of a 1.7 m solution of sodium chloride assuming 100% dissociation.  For water kbp=0.512 degree C/m and kfp = 1.86 degree C/m.

I don't know how to get melting point.  Is the difference between the change in freezing point and melting point?  Here's what I did so far.

:delta: Tbp =kbpmsol particles
:delta: Tbp = .512 C/m x 1.70 m
:delta: Tbp = .870 C

:delta: Tfp =kfpmsol particles
:delta: Tfp = .1.86 C/m x 1.70 m
:delta: Tfp = 3.16 C

Thanks for your help. 
You haven't considered dissociation of NaCl anywhere.

About the melting point thingy...
Hint : What is the solvent?
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Offline meghan

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Re: Help in calculating melting point
« Reply #2 on: February 28, 2010, 10:52:07 AM »
Thank you for the guidance.  I understand this now.    ;D

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