Question

Could someone tell me why the boiling point would decrease, other than decrease in pressure?

Answer 1

boiling point equals the temperature at which the vapor pressure of a liquid equals the atmospheric pressure

as height increases atmospheric pressure decreases. So, the vapor pressure does not need to be as great to equal the atmospheric pressure. And so boiling point decreases.

Answer 2

I was doing this in the lab and at 750 mm Hg......i need another reason and idk what. It was a distillation

Answer 3

pressure height purification? ... idk im not sure

Answer 4

it wasn't that high off the table

Answer 5

the solution was a mix between a ketone and alcohol

Answer 6

You can lower the boiling point of a substance by mixing it with another substance that has a lower boiling point to begin with (technically you're lowering the boiling point of the solution, but that's what distillation is all about). In your case, the alcohol will have a higher boiling point than the ketone due to hydrogen bonding, which keeps it in the liquid phase. Once you mix the ketone in, however, it disrupts the interactions between individual alcohol molecules, allowing more to enter the gas phase. This means the vapour pressure will reach atmospheric pressure at a relatively lower temperature, and that's what gives you the lower boiling point.

Hope that made sense!