Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: meghan on February 27, 2010, 08:45:27 AM

Title: Help in calculating melting point
Post by: meghan 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 k_bp=0.512 degree C/m and k_fp = 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:T_bp =k_bpm_{sol particles}
 :delta:T_bp = .512 C/m x 1.70 m
 :delta:T_bp = .870 C

 :delta:T_fp =k_fpm_{sol particles}
:delta:T_fp = .1.86 C/m x 1.70 m
:delta:T_fp = 3.16 C

Thanks for your help. 

Title: Re: Help in calculating melting point
Post by: Schrödinger on February 27, 2010, 01:10:39 PM

Quote from: meghan on February 27, 2010, 08:45:27 AM

Q: Calculate the melting point of a 1.7 m solution of sodium chloride assuming 100% dissociation.  For water k_bp=0.512 degree C/m and k_fp = 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: T_bp =k_bpm_{sol particles}
:delta: T_bp = .512 C/m x 1.70 m
:delta: T_bp = .870 C

:delta: T_fp =k_fpm_{sol particles}
:delta: T_fp = .1.86 C/m x 1.70 m
:delta: T_fp = 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?

Title: Re: Help in calculating melting point
Post by: meghan on February 28, 2010, 10:52:07 AM

Thank you for the guidance.  I understand this now.    ;D