Boiling-Point Elevation and Freezing-Point Depression Boiling-Point Elevation (∆T b ): The boiling...
-
Upload
chad-fisher -
Category
Documents
-
view
222 -
download
3
Transcript of Boiling-Point Elevation and Freezing-Point Depression Boiling-Point Elevation (∆T b ): The boiling...
Boiling-Point Elevation and Freezing-Point Depression
•Boiling-Point Elevation (∆Tb): The boiling point of the solution (Tb) minus the boiling point of the pure solvent (T°
b):
∆Tb = Tb – T°b
–∆Tb is proportional to concentration:
∆Tb = Kb m Kb = molal boiling-point elevation constant.
Boiling-Point Elevation and Freezing-Point Depression
•Freezing-Point Depression (∆Tf): The freezing point of the pure solvent (T°
f) minus the freezing point of the solution (Tf).
∆Tf = T°f – Tf
–∆Tf is proportional to concentration:
∆Tf = Kf m Kf = molal freezing-point depression constant.
Boiling-Point Elevation and Freezing-Point Depression
Boiling-Point Elevation and Freezing-Point Depression
Boiling-Point Elevation and Freezing-Point Depression
• The phase diagram shows a close-up of the liquid–vapor phase transition boundaries for pure chloroform.
a)Estimate the boiling
point of pure
chloroform.
a)Estimate the molal
concentration of the
nonvolatile solute.
Boiling-Point Elevation and Freezing-Point Depression
•van’t Hoff Factor, i: This factor equals the number of ions produced from each molecule of a compound upon dissolving.
–i = 1 for CH3OH i = 3 for CaCl2
–i = 2 for NaCl i = 5 for Ca3(PO4)2
•For compounds that dissociate on dissolving, use:
∆Tb = iKb m ∆Tf = iKf m ∆P = ix2 P°1