Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: iScience on November 01, 2013, 08:35:40 PM
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when boiling/evaporating a solution of a non-volatile solute, do some of the solute constituents still get kicked into the gas phase?
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Define "non-volatile"
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yes. Especially if boiling as aerosols will be generated.
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when boiling/evaporating a solution of a non-volatile solute, do some of the solute constituents still get kicked into the gas phase?
This also depends on your definition of the "gas phase" and "kicked into"
Non-volatile substances by definition won't become gaseous when boiling a liquid in which they are dissolved.
Please define your question more clearly, if you could provide an example then we can better refine our answers.
yes. Especially if boiling as aerosols will be generated.
408 makes a very good point if you define the gas phase as the space above the liquid rather than the substance being in it's gaseous state.
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sorry for the long delay;
Please define your question more clearly, if you could provide an example then we can better refine our answers.
a salt water solution. salt i thought was non-volatile. but every time i boil water water (for pasta), i can definitely smell the salt; (i don't know if it's actually the salt i'm smelling or something else, but it's a distinct smell vs when i just boil plane water.)
Non-volatile substances by definition won't become gaseous when boiling a liquid in which they are dissolved.
i thought non-volatile just meant that a substance doesn't easily evaporate at room temperature. Although, i still can smell the salt of a salt water solution at room temp.
This also depends on your definition of the "gas phase" and "kicked into"
let's start with the 'get kicked into' part. At the surface of say, a sugar water solution (i learned in gen chem that sugar (glucose) wasn't supposed to be volatile), whether or not the sugar molecule gets enough energy to get kicked up above the solution is temperature dependent. But assuming it does get kicked up above the solution, (i'm just "defining" 'kicked up' as just.. having enough kinetic energy to leave the solution surface), what determines whether it can enter the gas phase or not? your response, the defining "gas phase" part, gives me the impression that getting kicked up above the solution is in some way different than actually entering the gas phase. could you elaborate what the difference is? or have i misinterpreted?
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When you boil water, you form water vapor - water in the gas phase - as well as a mist. Water vapor is, strictly speaking, invisible because it does not absorb in the visible range to appreciable degree. The mist you see above boiling water is not water in the gas phase. It is an aerosol formed from mechanical action of bubbling (primary aerosol) as well as water vapor cooling/condensing when it hits the air (secondary aerosol).
If you put salt in water and boil the water, there is not enough heat to melt the salt. And in any case the salt is in a aqueous phase so "melting the salt" doesn't really mean a whole lot in any case. However salt can still end up in the air through primary aerosol formation - if water droplets/particles are ejected directly from the boiling solution, they will contain whatever solution was being boiled. Any secondary aersol that's formed is due to condensing water vapor, however, and these droplets cannot contain salt because there is no salt in the gas phase. I suspect that the majority of mist formed from boiling water, particularly high above the source, is due to secondary aerosol formation, but I'm not sure.
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thanks! i think that answers everything