Need explaination

[prsndwg]

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help me understand this please:


"When attractive forces between the mixed molecules are respectively weaker than those between the pure ones, molecules will more easily escape from the liquid surface. Consequently, the vapor pressure of solution becomes higher than expected, phenomenally known as the positive deviation."


I really thought a mixture will have a higher boilin point and a lower vapor presssure!

am I wrong or this is a different concept?😕😕


Thanks

 

[suhshi]

help me understand this please:


"When attractive forces between the mixed molecules are respectively weaker than those between the pure ones, molecules will more easily escape from the liquid surface. Consequently, the vapor pressure of solution becomes higher than expected, phenomenally known as the positive deviation."


I really thought a mixture will have a higher boilin point and a lower vapor presssure!

am I wrong or this is a different concept?😕😕


Thanks

i think the concept your talkin bout is related to Raoults Law

If you have two liquids A and B,if the intermolecular forces btw A and B ar weaker than those between A and A or btw B and B, then the molecules will escape from the liquid solution into the gas phase more easily than they would from pure A an pure B. Therefore, the their partial vapor pressures will be higher than predicted by Raoult's law.
Now most solutions deviate from Raoults Law.

Your right, vapor is usually depressed and boiling point is elevated. however, the concept that we are discussing is relating to that fact that many solutions deviate from Raoult's Law.

Hope it makes sense.

I would just mainly worry about thw equation used .

 

[prsndwg]

i think the concept your talkin bout is related to Raoults Law

If you have two liquids A and B,if the intermolecular forces btw A and B ar weaker than those between A and A or btw B and B, then the molecules will escape from the liquid solution into the gas phase more easily than they would from pure A an pure B. Therefore, the their partial vapor pressures will be higher than predicted by Raoult's law.
Now most solutions deviate from Raoults Law.

Your right, vapor is usually depressed and boiling point is elevated. however, the concept that we are discussing is relating to that fact that many solutions deviate from Raoult's Law.

Hope it makes sense.

I would just mainly worry about thw equation used .

understandable..thanks