Boiling Elevation/Melting Depression

[sinned]

---

Members do not see this ad.

I know that boiling point elevation and melting point depression is a colligative property, therefore the equation is Tf = i (Kf) m. The "i" in the equation is the dissociation of solute particles, so for example, if NaCl is added to the solution, would "i" be equal to 2 in the equation? Since it dissociates into two particles Na+ and Cl-? What about HCl?

If possible, can you guys elaborate and give me some other examples if your comfortable with this expression?

Thanks,
Den

 

[chordata]

Just an FYI...I've seen a lot of people make this mistake in my Chem Class and it is possible the DAT might try to do the same.

Melting point depression is not a colligative property. Freezing point depression, on the other hand, is.

 

[sinned]

Ooops I meant Freezing point depression...anyways, can anyone answer my question? Plssss...

 

[E. coli]

I know that boiling point elevation and melting point depression is a colligative property, therefore the equation is Tf = i (Kf) m. The "i" in the equation is the dissociation of solute particles, so for example, if NaCl is added to the solution, would "i" be equal to 2 in the equation? Since it dissociates into two particles Na+ and Cl-? What about HCl?

If possible, can you guys elaborate and give me some other examples if your comfortable with this expression?

Thanks,
Den

It depends on the polarity of the molecule. Electrolytes produce ions when dissolved in solution. Nonelectrolytes does not produce ions when dissolved in solution.

For example,
NaCl is ionic and therefore dissociates into Na+ and Cl- in solution. (i = 2)
HCl is polar covalent molecule and therefore dissociates into H+ and Cl-. (i = 2)
However, if a molecule is nonpolar (i.e. C11H22O11), then the molecule would not dissociate (i = 1).

I hope this helps!

 

[sinned]

thank you, I wanted some clarity so im not wishy washy when such a question pops up...