Which has the highest boiling point and lowest freezing point?

(a) 0.4 m NaCl

0.3 m Na2SO4

0.5 m sucrose (nonelectrolyte)


(b)0.2 m HCl

0.2 m acetic acid

0.3 m KOH (weak electrolyte)

(c) 0.5 m ethylene glycol (nonelectrolyte)

0.4 m glucose (nonelectrolyte)

0.3 m BaCl2



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(a) Highest BP: .4m NaCl
Lowest FP: .5 m surcrose

(b) Highest BP: ..3m KOH
Lowest FP: .2m acetic acid

(c) Highest BP: .3m BaCl2
Lowest FP: I am unsure

Could someone check this for me?? Thank you!!!

How did you arrive at these answers. If you used

delta T = i*Kb*m and
delta T = i*Kf*m it seems to me that the material having the highest boiling point and the material having the lowest freezing point must be the same? And you have two answers for each. The secret is i*m.

By the way, KOH is not a weak electrolyte. Just the contrary.

a) the one that has the highest bp (and lowest fp, and remember, that solution will be both. Lowest FP means greatest fp depression). Doesn't the effective molality i*m depend on the number of particles, NaCl is 2, Na2So4 is three, and sucrose is one. I don't agree with your answer.

b) HCl completely (almost) dissociates, into 2 particles per molecule, the others hardly dissociate at all.
c)BaCl2 breaks into 3 particles per molecule

Im really sorry. Im actually looking for the highest and lowest boiling points. I typed it wrong.

ok. So i*m is still the secret.

For a.
NaCl = 0.4 m. i=2 i*m=0.8
Na2SO4 = 0.3m. i=3 i*m=0.9
sucrose = 0.5m. i=1 i*m=0.5
So the highest boiling point will be the one that has the highest i*m which is Na2SO4. The lowest boiling point will be the lowest i*m which is sucrose.
Part b and c are done the same way.
b is correct.
c is not.
i for ethylene glycol is 1.
i for glucose is 1.
i for BaCl2 is 3.

To determine the highest boiling point (BP) and lowest freezing point (FP) among the given options, we need to consider the concept of colligative properties.

Colligative properties depend on the number of particles (ions or molecules) present in a solution, rather than the specific identity of the solute. These properties include boiling point elevation and freezing point depression.

For boiling point elevation, the solute with the highest concentration of particles will have the highest boiling point. For freezing point depression, the solute with the highest concentration of particles will have the lowest freezing point.

Let's analyze each option:

(a) In this case, we have:
- 0.4 m NaCl: This will dissociate into Na+ and Cl- ions, providing 2 particles; therefore, it has the highest boiling point.
- 0.3 m Na2SO4: This will dissociate into 3 particles; therefore, it has a lower boiling point than NaCl.
- 0.5 m sucrose: Since it is a nonelectrolyte, it does not dissociate, providing only 1 particle; therefore, it has the lowest boiling point. As for the freezing point, the sucrose will have the highest freezing point as it doesn't dissociate and therefore doesn't contribute to the depression of freezing point.

(b) For this case:
- 0.2 m HCl: This will dissociate into H+ and Cl- ions, providing 2 particles.
- 0.2 m acetic acid: This molecule does not fully ionize and provides less than 2 particles.
- 0.3 m KOH: This weak electrolyte will partially dissociate into K+ and OH- ions, providing more than 2 particles, so it has the highest boiling point.
- As for the freezing point, acetic acid will have the lowest freezing point because it doesn't dissociate and therefore doesn't contribute to the depression of freezing point.

(c) In this case:
- 0.5 m ethylene glycol: As a nonelectrolyte, it does not dissociate, providing only 1 particle.
- 0.4 m glucose: Also a nonelectrolyte, it provides only 1 particle.
- 0.3 m BaCl2: This compound will dissociate into Ba2+ and 2 Cl- ions, providing 3 particles. Thus, it has the highest boiling point.
- For the freezing point comparison, we can't determine the exact order without additional information. The freezing point depression will depend on factors such as the nature of the solvent and the solute.

In summary, the highest boiling point is found in option (a) with 0.4 m NaCl, and the lowest freezing point is found in option (a) with 0.5 m sucrose. However, we cannot determine the lowest freezing point from option (c) due to the unknown nature of the solvent and the solute.