Confusion: Freezing point depression, boiling point elevation

[DentalLonghorn2014]

Hi everyone,

I have a few gaps in my notes somehow and I think I've confused myself on this topic. Please confirm?

The greater the [ions], the greater the freezing point depression.
The lower the [ions], the higher the boiling point elevation.

So...greater freezing point depression = lower freezing point
If something is least depressed, does that = higher freezing point or higher BP elevation?

Is this accurate or am I going crazy? lol

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[qkrdpsk]

Greater [ion] = Greater FP depression = lower FP
Greater [ion] = greater BP elevation = higher BP

Something that's least depressed has the highest FP.

 

[DentalLonghorn2014]

Greater [ion] = Greater FP depression = lower FP
Greater [ion] = greater BP elevation = higher BP

Something that's least depressed has the highest FP.

How can something with greater ion concentration have both a higher FP depression and BP elevation?

 

[hockey553]

Hi everyone,

I have a few gaps in my notes somehow and I think I've confused myself on this topic. Please confirm?

The greater the [ions], the greater the freezing point depression.
The lower the [ions], the higher the boiling point elevation.

So...greater freezing point depression = lower freezing point
If something is least depressed, does that = higher freezing point or higher BP elevation?

Is this accurate or am I going crazy? lol

I think you are not understanding why freezing point lowers and the boiling point increases. The freezing point decreases when ions are dissolved is because the intermolecular forces between the solute and solvent increases and this interferes with the ability for the solution to freeze. The boiling point increases because there are additional forces with the solute and solvent. These additional forces means more energy is needed for the solution to boil.

 

[scout1992]

A simple way to remember this is that more ions = more extreme freezing/ boiling point. The freezing point gets colder and the boiling point gets hotter, in other words.

 

[DentalLonghorn2014]

I think you are not understanding why freezing point lowers and the boiling point increases. The freezing point decreases when ions are dissolved is because the intermolecular forces between the solute and solvent increases and this interferes with the ability for the solution to freeze. The boiling point increases because there are additional forces with the solute and solvent. These additional forces means more energy is needed for the solution to boil.

Oh this makes more sense. Thank you!

 

[DentalLonghorn2014]

A simple way to remember this is that more ions = more extreme freezing/ boiling point. The freezing point gets colder and the boiling point gets hotter, in other words.

Thank you!!

 

[qkrdpsk]

If you add ions into let's say water, you get increase in IMF between the water molecules & ions making it harder to freeze thus solution must be cooled to even lower temp, meaning greater FP depression (FP goes down more). Additional IMF also leads to greater BP elevation (BP goes up more)

 

[DentalLonghorn2014]

If you add ions into let's say water, you get increase in IMF between the water molecules & ions making it harder to freeze thus solution must be cooled to even lower temp, meaning greater FP depression (FP goes down more). Additional IMF also leads to greater BP elevation (BP goes up more)

Gracias!