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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: naved_s9994 on July 31, 2009, 10:16:38 pm

Title: Unit 2
Post by: naved_s9994 on July 31, 2009, 10:16:38 pm

A solute __________________ of the solvent.   
    a.   raises the freezing point   
    b.   raises the boiling point   
    c.   lowers the boiling point   
    d.   does not affect

Can you explain why also... thanks!

Title: Re: Unit 2
Post by: Edmund on July 31, 2009, 10:53:50 pm

B.

Using the Boiling-Point elevation formula,

Change in Temp = K . m

where the Change in Temp is the difference in the boiling point of the solution (with solute) and solution (without solute), K is the boiling point constant, and m is the molality.

When an amount of solute is added, molality increases, so change in temp increases too, therefore we expect a higher boiling point...

Hope it makes sense?

Title: Re: Unit 2
Post by: lukeperry91 on July 31, 2009, 11:09:10 pm

When i used to get these questions in year 11, I would just think about the ocean... its harder to freeze/boil it (hence you can have subzero temps in the arctic and why steam doesn't fly off due to evaporation). Edmund's explanation sounds alot more scientific though :P

Title: Re: Unit 2
Post by: naved_s9994 on August 01, 2009, 09:13:57 am

yea thanks both!
Edmund +1 :P