[Needaask]

Are aqueous solutions just having a solute dissolved in a solvent. So If I had a ethanol in water, the ethanol is the solute while the water is the solvent right? So would I say that water now is also aqueous because they are dissolved by the ethanol also right? So why is it that if ethanol reacts with water, water is written as a liquids and not aqueous.

What if I have a solvent that is not water. Say ethanol and methanol. What would be the case here? So I'm quite confused on what an aqueous solution means as Wikipedia only states that aqueous is only when the solute is dissolved in water. But for concentration it seems

In the first the concentration of ethanol would be number of moles of ethanol/total volume and for water would it just be number of moles of water/total volume? And a similar case for the second case with methanol and ethanol?

So I'm quite confused on what is what. Because in many concepts such as reactions having a high concentration would mean a faster rate of reaction. So say if the ethanol and water reacts with each other then if I added more methanol then won't the total volume increase as well? So what do these term actually mean?

Thanks for the help

[Borek]

Aqua means water in Latin. So aqueous solution means something dissolved in water, not in any liquid solvent.

[Arkcon]

You have made a long posting, with a trivial topic name, trying to cover many points, that are often wrong.  I'll try to help point by point -- but you should try to have a clearer question, to start with.

Are aqueous solutions just having a solute dissolved in a solvent.

No.  That is not the definition.  You can look up the definition, and see if it stops you from making mistakes.  Look at the work 'aqueous' -- you can see the Latin root aqua inside it.  What does that mean? *EDIT* Borek: beat me to this one.  But work with the rest

So If I had a ethanol in water, the ethanol is the solute while the water is the solvent right?

That is perfectly correct to say. 

So would I say that water now is also aqueous because they are dissolved by the ethanol also right?

That is not correct to say, because you're using the wrong definition for aqueous.  Further conclusions, based on this, and your first statement are automatically wrong, even if you say something correct in between.

So why is it that if ethanol reacts with water, water is written as a liquids and not aqueous.

Two problems here: why did you suddenly mention reactions, when you were previously talking about solutions?  I'm missing some information, that lead to the new conclusion.  I can't say you're wrong or right, and you can end up correct when you fill it in later.  That's not a good way to ask questions. And you also seem to not have the definition correct here.

What if I have a solvent that is not water. Say ethanol and methanol. What would be the case here?

So many possible answers.  OK.  Lets just say, not aqueous.  We can even say, 'anhydrous', if there's no water present, not even a bit of moisture.  You may be new to this, but you get very different chemistry when there's no water.  Its good for you to know that in advance.

So I'm quite confused on what an aqueous solution means as Wikipedia only states that aqueous is only when the solute is dissolved in water.

Halle-freaking-lujah, you did know the definition of aqueous.  Why did you use a different one for most of this post?  Why did you almost use it correctly once, regarding ethanol in water, not wrong at all times if you made a definition error?

But for concentration it seems

OK, now an unrelated question.  OK.  I can answer two, no problem ... but, you don't think the definitions above somehow change how concentrations are determined.  Because they don't.  You can't say they're connected in any way.

In the first the concentration of ethanol would be number of moles of ethanol/total volume and for water would it just be number of moles of water/total volume? And a similar case for the second case with methanol and ethanol?

Sure.  Why not try a specific example, so we can see what you mean.

So I'm quite confused on what is what. Because in many concepts such as reactions having a high concentration would mean a faster rate of reaction. So say if the ethanol and water reacts with each other then if I added more methanol then won't the total volume increase as well? So what do these term actually mean?

There's lots here, and I don't really know what you're asking.  Again, a more specific question will help us understand what you don't understand.

Thanks for the help

Shine on you crazy diamond.

[Needaask]

Oh ok! Say a liquid A is dissolved in a solvent B. So either of them wouldn't be considered aqueous as neither of them is water. And now say A reacts with another substance. So having a high concentration of A would mean that the rate of reaction would be faster right? But if we were to write the equation it would be A(l)+X Y+Z.

So if I was not given the information that A was dissolved I wouldn't have known if A was a pure liquid or a dissolved liquid?

Thanks again

[Needaask]

Or if now I were to use water say this HA(aq)+H₂O (l) H₃O⁺(aq)+A^-(aq) so now if I were to add in more water the concentration of the aqueous HA would decrease. But what about the water itself? Since now the concentration of H₂O(l) is number of moles of H2O/volume of solution where both n and V increases, I'm not sure if the concentration increases.

I'm actually not sure if there is a concentration of water because while learning about the Kc stuff, they said that water being a liquid has a fixed concentration. So what i thought (the concentration of water thing from the above paragraph) seems to contradict with the reasoning KC gave. That's why I'm quite clueless about this whole 'concentration' thing.

Thanks! brilliant magma? (Cos diamonds are brilliant and magma is crazy hot so word play? Haha)

Edit: ohh Pink Floyd

[Big-Daddy]

As far as I can tell, when ethanol is dissolved in water all this really means is that ethanol is mixed in enough water that the ethanol particles have been broken up so there are negligible intermolecular forces between them. If you've got enough ethanol present, some will be liquid (because it clumps together - it can't all get dissolved), some will be dissolved. The formation of the liquid begins when the Ksp of ethanol is reached; below this limit, all added ethanol is dissolved. After that limit there is the equilibrium established between ethanol dissolved in water, and ethanol "liquid" mixed with the water, the distinction being that the dissolved ethanol is not clumped together in its liquid form anymore.

There should also be some equilibrium of water being liquid as opposed to being dissolved in the (liquid - you cannot dissolve something in a solute) ethanol. But this might have a much lower Ksp and thus much more water will be liquid as opposed to dissolved in ethanol, than ethanol will be liquid and dissolved in water.

[Needaask]

As far as I can tell, when ethanol is dissolved in water all this really means is that ethanol is mixed in enough water that the ethanol particles have been broken up so there are negligible intermolecular forces between them. If you've got enough ethanol present, some will be liquid (because it clumps together - it can't all get dissolved), some will be dissolved. The formation of the liquid begins when the Ksp of ethanol is reached; below this limit, all added ethanol is dissolved. After that limit there is the equilibrium established between ethanol dissolved in water, and ethanol "liquid" mixed with the water, the distinction being that the dissolved ethanol is not clumped together in its liquid form anymore.

There should also be some equilibrium of water being liquid as opposed to being dissolved in the (liquid - you cannot dissolve something in a solute) ethanol. But this might have a much lower Ksp and thus much more water will be liquid as opposed to dissolved in ethanol, than ethanol will be liquid and dissolved in water.

Ohh so because only a little water actually does interact with the ethanol while for ethanol all of it has interacted so we would say ethanol is dissolved but for water we would say that it's still a liquid? So if I were to find a scenario as you mentioned where water is the one being dissolved then the other liquid (the solvent) would be considered s liquid still?

So are all solvents like this whereby there are considered to be liquids?

Thanks BD!

[Corribus]

Just so you know, when you're mixing one liquid into another, it's not always so easy to distinguish solute from solvent, particularly when the two liquids are indefinitely miscible.  It may be more appropriate to speak of mixtures more generally in this case.  Reason being that in this case the solute and solvent are both of the same phase, and so there's often no easily distinguished point of maximum solubility. 

For instance, take 100% water and start adding ethanol.  You add more and more ethanol until the mixture is over 50% ethanol.  At what point did it cease being a solution of ethanol in water and begin being a solution of water in ethanol?  50/50?  Then the distinction is purely semantics.  Moreover, ethanol and water form an azeotropic mixture at some relative proportions, so normal "solid in liquid solution behavior" is not observed.  Or, at least, we use a different body of terminology to refer to many of the same or similar physical effects.

[Needaask]

Just so you know, when you're mixing one liquid into another, it's not always so easy to distinguish solute from solvent, particularly when the two liquids are indefinitely miscible.  It may be more appropriate to speak of mixtures more generally in this case.  Reason being that in this case the solute and solvent are both of the same phase, and so there's often no easily distinguished point of maximum solubility. 

For instance, take 100% water and start adding ethanol.  You add more and more ethanol until the mixture is over 50% ethanol.  At what point did it cease being a solution of ethanol in water and begin being a solution of water in ethanol?  50/50?  Then the distinction is purely semantics.  Moreover, ethanol and water form an azeotropic mixture at some relative proportions, so normal "solid in liquid solution behavior" is not observed.  Or, at least, we use a different body of terminology to refer to many of the same or similar physical effects.

Oh! So how should we classify them? Because I'm not too sure how to use them in some of those Kc stuff where the concentrations of the substances are important. For liquids and solids in heterogeneous solutions they aren't included. So when this comes along I'm not too sure how to classify them.

So what if I dissolved a solid, A in ethanol? How would I represent this because now I wouldn't be allowed to write ti as A(aq).

Thanks for the help

[AWK]

Why not A(EtOH)?

[Needaask]

Why not A(EtOH)?

We can do that? That would help a lot because I thought we would just label it as (s). What about the ethanol and water case? How would we approach that? Because in heterogeneous reactions the solids and liquids have a fixed concentration so I'm not too sure how to deal with those 2 liquids type of scenario.

Thanks

[Corribus]

It doesn't really matter what you call it.  It's just a matter of bookkeeping so you know it's dissolved in something, rather than a large chunk of solid.  It's the latter distinction that is important, because chemical activity of a large particle is different than the activity of a fully dissolved species.

[Needaask]

It doesn't really matter what you call it.  It's just a matter of bookkeeping so you know it's dissolved in something, rather than a large chunk of solid.  It's the latter distinction that is important, because chemical activity of a large particle is different than the activity of a fully dissolved species.

Oh I get it. BTW in the second sentence do you mean that the activity of a solid is different from a dissolved solute?

Also going back into the ethanol and water case, how would i look into it? Would that be considered liquids or dissolved substances?

It's because I was going through my notes on chemical equilibrium and the distinction of whether it is a liquid seems very important. They stated that for heterogeneous reactions liquids and solids have a constant concentration. What does that mean and how does it apply in these scenarios?

In a case where say CH3COOH(aq)+H2O(l) CH3COO^-(aq)+H3O⁺(aq) I would agree that the water here is a liquid and not a dissolved substance by using BD's explanation that most of the H2O remains by themselves making it a liquid. What does it mean by the concentration of my liquid water is fixed - because in the first few post i thought that concentration would be Moles of water/Total volume which makes it not fixed. 

So I'm not too sure about this 2 questions which are somewhat related with each other.

Thanks Corribus

[Big-Daddy]

Ohh so because only a little water actually does interact with the ethanol while for ethanol all of it has interacted so we would say ethanol is dissolved but for water we would say that it's still a liquid? So if I were to find a scenario as you mentioned where water is the one being dissolved then the other liquid (the solvent) would be considered s liquid still?

So are all solvents like this whereby there are considered to be liquids?

Thanks BD!

Well by definition of the CH₃CH₂OH being dissolved, the particles have been broken up so that one ethanol molecule is surrounded by several water molecules, preventing there from being any serious intermolecular forces between the ethanol molecules, so that the ethanol is broken up from being a liquid, into individual molecules floating around inside the water. I'm sure you can conceptualize that, if one ethanol molecule is surrounded by several water molecules (and I mean, a lot), then water has not been that much changed - there's just the odd ethanol molecule where we would find a water molecule before, but mostly still water - so we call it liquid. Meanwhile, the ethanol has been changed hugely - where a single ethanol molecule was previously surrounded by other ethanol molecules, now it's been broken apart from them and is surrounded by water - and thus we call it dissolved, in water solution, which is known as aqueous solution.

If there is significant amount of ethanol present, now we'll get an equilibrium, CH3CH2OH (l)  CH3CH2OH (dissolved in water). Some ethanol will be liquid and mixed with the water, because there isn't enough water to surround each molecule and pull it apart. And if you've got enough ethanol, then we can get another equilibrium forming, H2O (l)  H2O (dissolved in ethanol), as within the liquid ethanol some water starts getting pulled apart and surrounded by ethanol. You can easily have both of these equilibria going on at once. I have to clarify my understanding on K_sp, but the impression I get is that, imagine we're adding ethanol, only once the K_sp limit is reached is there any formation of liquid ethanol (until then, all that is added is dissolved - though maybe this is a bit of an approximation, I don't know?). And then we start getting liquid water becoming dissolved in the liquid ethanol, though most of the water may still be liquid rather than dissolved. And finally, by this logic, we will reach a stage where the K_sp ratio of water in ethanol is no longer met, and from then on there is no liquid water and all the water is dissolved in the liquid ethanol. It also makes logical sense that as more water is dissolved in ethanol as opposed to being liquid, the liquid water will have fewer and fewer molecules and thus will be able to dissolve less and less of the ethanol that it previously had dissolved, which furthers the conversion of ethanol dissolved in water to liquid ethanol as we add ethanol.

[Needaask]

Ohh so because only a little water actually does interact with the ethanol while for ethanol all of it has interacted so we would say ethanol is dissolved but for water we would say that it's still a liquid? So if I were to find a scenario as you mentioned where water is the one being dissolved then the other liquid (the solvent) would be considered s liquid still?

So are all solvents like this whereby there are considered to be liquids?

Thanks BD!

Well by definition of the CH₃CH₂OH being dissolved, the particles have been broken up so that one ethanol molecule is surrounded by several water molecules, preventing there from being any serious intermolecular forces between the ethanol molecules, so that the ethanol is broken up from being a liquid, into individual molecules floating around inside the water. I'm sure you can conceptualize that, if one ethanol molecule is surrounded by several water molecules (and I mean, a lot), then water has not been that much changed - there's just the odd ethanol molecule where we would find a water molecule before, but mostly still water - so we call it liquid. Meanwhile, the ethanol has been changed hugely - where a single ethanol molecule was previously surrounded by other ethanol molecules, now it's been broken apart from them and is surrounded by water - and thus we call it dissolved, in water solution, which is known as aqueous solution.

If there is significant amount of ethanol present, now we'll get an equilibrium, CH3CH2OH (l)  CH3CH2OH (dissolved in water). Some ethanol will be liquid and mixed with the water, because there isn't enough water to surround each molecule and pull it apart. And if you've got enough ethanol, then we can get another equilibrium forming, H2O (l)  H2O (dissolved in ethanol), as within the liquid ethanol some water starts getting pulled apart and surrounded by ethanol. You can easily have both of these equilibria going on at once. I have to clarify my understanding on K_sp, but the impression I get is that, imagine we're adding ethanol, only once the K_sp limit is reached is there any formation of liquid ethanol (until then, all that is added is dissolved - though maybe this is a bit of an approximation, I don't know?). And then we start getting liquid water becoming dissolved in the liquid ethanol, though most of the water may still be liquid rather than dissolved. And finally, by this logic, we will reach a stage where the K_sp ratio of water in ethanol is no longer met, and from then on there is no liquid water and all the water is dissolved in the liquid ethanol. It also makes logical sense that as more water is dissolved in ethanol as opposed to being liquid, the liquid water will have fewer and fewer molecules and thus will be able to dissolve less and less of the ethanol that it previously had dissolved, which furthers the conversion of ethanol dissolved in water to liquid ethanol as we add ethanol.

Ohh so at low concentrations its as if the water is still a liquid as most of it is water and only a few molecules of ethanol is present in the whole thing. So the concentration doesn't really change if I add more water?

But if I were to add more ethanol into water in this case, why would the change in concentration be significant?

Also, in the case of having really a lot of ethanol (like the 50/50 ratio Corribus mentioned earlier), then how should they be considered? Like if I were to add in more water would the concentration change a lot or very little?

Thanks BD for the great reply