Can someone explain the relationship of VP with BP,MP and FP

[Mp07d]

---

Members don't see this ad.

how does vapor pressure correlate with boiling,melting and freezing point?

For example, decreasing VP increases BP ect ect

 

[ilovemcat]

how does vapor pressure correlate with boiling,melting and freezing point?

For example, decreasing VP increases BP ect ect

Basically, when you add a substance to a solution, for example, NaCl in water , it changes some of the properties of the solution.

After NaCl gets dissolved in the water, the Vapor Pressure decreases (ie, VP depression) because the dissolved ions increase the intermolecular bonds of the solution via ion-dipole interactions. Therefore, fewer molecules can escape into the gas phase.

Another effect is Freezing Point depression (FP goes down) because the liquid can crystallize easier with the ions present in the solution. Rather than forming a perfect crystal, the water molecules crystallize around the ions. As a result, the liquid freezes under lower temperatures than normal and therefore melts at lower temperatures as well.

Boiling Point Elevation - BP goes up because VP goes down. A liquid will begin to vaporize or boil when the vapor pressure of a solution equals atmospheric pressure. If you lower or depress the vapor pressure of a solution by adding ions, then it will be more difficult to boil (ie, it elevates the boiling point.)

 

[Mp07d]

Thanks man.

and in terms of colligative properties...

the higher the concentration = higher bp

but higher concentration = lower fp and mp right?

 

[PiBond]

Basically, when you add a substance to a solution, for example, NaCl in water , it changes some of the properties of the solution.

After NaCl gets dissolved in the water, the Vapor Pressure decreases (ie, VP depression) because the dissolved ions increase the intermolecular bonds of the solution via ion-dipole interactions. Therefore, fewer molecules can escape into the gas phase.

Another effect is Freezing Point depression (FP goes down) because the liquid can crystallize easier with the ions present in the solution. Rather than forming a perfect crystal, the water molecules crystallize around the ions. As a result, the liquid freezes under lower temperatures than normal and therefore melts at lower temperatures as well.

Boiling Point Elevation - BP goes up because VP goes down. A liquid will begin to vaporize or boil when the vapor pressure of a solution equals atmospheric pressure. If you lower or depress the vapor pressure of a solution by adding ions, then it will be more difficult to boil (ie, it elevates the boiling point.)

it's my understanding that ions present in solution make the crystallization more difficult since they interfere with the lattice formation. thus, a lower temperature is necessary to achieve freezing

Thanks man.

and in terms of colligative properties...

the higher the concentration = higher bp

but higher concentration = lower fp and mp right?

sounds like you got it. as molality increases the deviation from BP/MP will increase as well. deltaT = (i)m(Kb)