Cracking of hydrocarbons and boiling point of salt water

[sgstudent]

Can alkenes be cracked or only alkanes can be cracked? Then what would the products be? Like for alkanes a alkenes must always be formed but what about for alkenes cracking?

Also, when we boil salt water its temperature is 101.4 degrees. But when performing fractional or simple distillation why dots the reading at the thermometer be 100 degrees even though the boiling point is 101.4?

Thanks for the help guys!

 

[Jasoni22]

Alkenes can be cracked as well. An example would be cracking butene to yield propene and ethene.

As for distillation, when you combine two immiscible liquids (such as water and alkanes/alkenes), the total vapor pressure of the mixture is the sum of the vapor pressures of the different liquids in the mixture. The result of this is that, as long as the mixture is being stirred, the boiling point of the mixture will be lower than the boiling points of any of the liquids if they were pure.

 

[Borek]

when you combine two immiscible liquids (such as water and alkanes/alkenes), the total vapor pressure of the mixture is the sum of the vapor pressures of the different liquids in the mixture. The result of this is that, as long as the mixture is being stirred, the boiling point of the mixture will be lower than the boiling points of any of the liquids if they were pure.

I don't see how it addresses the question, NaCl is not a liquid immiscible with water.

 

[Jasoni22]

I was assuming that the distillation was of hydrocarbons mixed in water, since you wouldn't perform fractional distillation of mere salt water with nothing else in it.