How do you determine electrical conductivity, freezing point, and pressure of water vapor for these compounds?

Question

If you could provide explanations as well as answers to the following questions, that would be great. Thanks!

Answer the following questions, which refer to 100 mL samples of 0.10 M aqueous solutions at 25°C of NaF, MgCl2, C2H5OH and CH3COOH.

a) Which solution has the lowest electrical conductivity? Explain.

b) Which solution has the lowest freezing point? Explain using both qualitative and quantitative reasoning.

c) Above which solution is the pressure of water vapor greatest? Explain.

(PS - I know I asked this question already, but someone answered it with some "do your homework yourself" answer and that was the only response I got. I really need help with this one, so I'm posting it again in hopes of an actual answer.)

Answer 1

go to tutor.com if you want good answers all the time or brain fuse  (they're tutoring sites) and they're there to help you.

we just browse for fun... but this one is kinda interesting so...

a . lowest electrical conductivity : if it dissociates the most, then it's the most, so less it dissociates the less it's conductive.

now i'm assuming you're putting in this in water as the solvent

NaF is strong

MgCl2 is strong

both those are ionic bonds, fall right off of each other.

C2H5OH is somewhat non polar

CH2COOH is also largely non polar but it is a carboxylic acid... so it will dissociate more

so best answer is C2H5OH the ethanol

b. freezing point... hm... i think it relates to dissociation again ... but exact opposite reasoning

the more it dissociates the more it's going to lower freezing point.

this is the freezing point depression or melting point depression

the formula is as such: delta T = kf x i x m... i is the dissociation = amount of ions coming off... larger i, the lower FP

NaF  i= 2

MgCl2 i = 3

others are somewhat nonpolar so not all of it will dissolve in water.

\MgCl2

c. i forget the concept behind it, but it's about holding the water molecule down and relates to boiling temperature since boiling point is reacted when the vapor pressure is equal to the atmospheric pressure.

so an educated guess, would be the BP elevation.

delta T = kb x i x m

the greater i is the higher temp it'll boil at.

which means the lower water vapor allowed at 100 deg c.

so... to allow greatest vapor pressure, you want the smallest "i" so C2H5OH

(a guess, but a pretty reasonable guess)

good luck, and hope i helped