This is for my teacher.

[shabnam]

Hi.I'm new here.I'm in a bit of a mess with my bio teacher.Here's my question-- Say I take a U-tube and fill one limb with pure water and the other with pure alcohol.They are seperated by a semi-permeable membrane.Shall osmosis take place?

My teacher thinks it won't but I believe it will.Could you sort it out.

Thanks!!!

[ecoli]

Why does your teacher think that it wouldn't?

[YT2095]

is it Absolute alcohol (100% pure) that you`re talking about? or the azeotrope?

[Klaynos]

I'd have thought as it is semi-permeable then, yes it will occur because the chemical potential will be different on both sides...

[shabnam]

He thinks that because the solvents are different they shouldn't get through.

But my argument is that as the two liquids are soluble in each other osmosis should occur.But I can't convince him.I'm trying to be more technical...

Thanks

[shabnam]

Its pure alcohol. er....whats an azeotrope?

[shabnam]

I'd have thought as it is semi-permeable then, yes it will occur because the chemical potential will be different on both sides...

OK. Think I get you.Thanks. But I'm not really confident about being able to explain chemical potential.Could you help me out?

[Klaynos]

How permeable is semi-permeable? What's the biggest thing it'll let through? That's the real question here.

 

tbh despite having an exam on statistical mechanics yesterday about this it's probably my most physics subject

 

The original gibbs statement was:

 

If to any homogeneous mass in a state of hydrostatic stress we suppose an infinitesimal quantity of any substance to be added, the mass remaining homogeneous and its entropy and volume remaining unchanged, the increase of the energy of the mass divided by the quantity of the substance added is the potential for that substance in the mass considered.

 

But what this means is a bit more complicated. I've always seen it as the lowest energy level that a system wants to tend to. It's used with the number of molecules in the statistical mechanics energy of a system to allow for open system.

 

If you minimise the gibbs free energy you can show that a requirement of a 2 level system for a minimal gibbs (so in equilibrium) the mew's of the 2 systems must be the same.

[John Cuthber]

If the membrane will let both alcohol and water through then ,in the log run, all you will get is a mixture of the 2 due to diffusion.