Colligative Properties (TPR Test 1)

[Synapsis]

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20. Which of the following is an example of a colligative property?
I. Vapor Pressure
II. Electrical Conductivity
III. Osmotic Pressure

As I took this FL, I saw this as a free point, picked I, II, and III, and moved on. The answer is I and III. Now, in GChem book 2, TBR explicitly states that conductivity is a colligative property and depends on the concentration of impurities in solution (just like the other colligative properties). TPR's explanation says that Vapor Pressure, Osmotic Pressure, BP Elevation, and MP Depression are the only colligative properties. Which one is correct?

I'm inclined to agree with TBR. More dissolution of an ionic impurity allows for greater conductance because the ions allow electrons to pass more readily. No ions means very little conductivity (like in pure water). Therefore, conductance is clearly a property that can depend on the number, or concentration, or dissolved solutes. Opinions?

 

[onedirection]

Colligative properties have nothing to do with the concentration of an ion

it's about specific ions

like how many ions does it dissociate to
The concentration doesn't matter

H2SO4 dissociates into 3 ions; that's what it means

being 3 molar has no influence on the colligative properties

the i value that you see determines the colligative properties and it's the # of ions it dissociates into

 

[Synapsis]

Colligative properties have nothing to do with the concentration of an ion

it's about specific ions

like how many ions does it dissociate to
The concentration doesn't matter

H2SO4 dissociates into 3 ions; that's what it means

being 3 molar has no influence on the colligative properties

the i value that you see determines the colligative properties and it's the # of ions it dissociates into

This just isn't correct. At least, it's not complete.

Yes van't hoff factor is important but so is the molality and molarity (for osmotic pressure). For example, just because NaCl dissociates into two ions doesn't just mean the boiling point will rise a certain amount. Adding one speck of NaCl does nothing, but adding a large amount significantly changes the boiling point. It's about dissociation and amount of impurity.

 

[onedirection]

Presence of the Van't hoff factor (couldn't remember the name) indicates it's a colligative property

http://en.wikipedia.org/wiki/Colligative_properties right at the start; electro whatever isn't included on this list

 

[Synapsis]

Yes but TBR argues that it is. I also just checked with two chem professors at my school who agree that it is, and I think I'll take all of that over wikipedia lol.