Freezing point depression lab

  • #1
ada15
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Hi Guys,

I have a question and its regarding to the freezing point depression lab ... I did an experiment where I had to find an "i" value for KCl. I'm getting 2.4 for "i" ... but the theoratical value is 2.

I was just wondering why expriment value os higher than the theortical value ? what would be the reason behind this?

Also, is there any website where I can find out that how the freezing point dpression graph look like for KCl?

Thanks
 
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Answers and Replies

  • #2
siddharth
Homework Helper
Gold Member
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I have a question and its regarding to the freezing point depression lab ... I did an experiment where I had to find an "i" value for KCl. I'm getting 2.4 for "i" ... but the theoratical value is 2.

I was just wondering why expriment value os higher than the theortical value ? what would be the reason behind this?

What's 'i'? The van't hoff factor?

Look into your book for the physical significance of the van't hoff factor and the answer should be obvious
 
  • #3
Borek
Mentor
29,138
3,767
What's 'i'? The van't hoff factor?

Look into your book for the physical significance of the van't hoff factor and the answer should be obvious

Perhaps I am missing something, but I think it should be just 2...

Experimental error? Math?



 
  • #4
siddharth
Homework Helper
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Perhaps I am missing something, but I think it should be just 2...

Experimental error? Math?

Borek
-- \

Yep.

I was saying that if ada15 read up on the van't hoff factor, he/she would immediately know that theoretically it can't exceed 2 and therefore must be an experimental error or math.
 
  • #5
GCT
Science Advisor
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I remember getting a value of "i" that was much further away from the theoretical value, however, it was calculated from the equilibrium constant for an acid. What may have happened in your case is that you may have added an excessive amount of KCl. Another thing is that supercooling may have resulted in a decreased freezing point value...this was the case for our solution, the NaCl employed as an 'ice bath' to freeze the experimental solution had a graph of temperature versus time that showed an initial dip in the temperature and then rose to the 'real' freezing point temperature.
 

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