[jena]

Hi, I have a question that is related to a lab experiment on extraction. The question states:

In the extraction of an organic compound from a dilute aqueous solution, will the organic solvent form the upper or lower layer when each following solvents is used?

(a) Chloroform
    My Answer: Upper layer

(b) Cyclohexane
     My Answer:Will form on the lower layer beacuse it is a hydrocarbon

(c) Heptane
     My Answer:Will form on the lower layer because it is a hydrocarbon

(d) Dichloromethane
      My answer:Will form on the lower layer

Are my answer correct. If not please explain where I may have gone wrong.

Thank you  

[Mitch]

Review the concept of density and it should be clear enough from there.

[jena]

Hi, you asked me to review the concept of density. So the organic layer is the layer that has the greater density than the aqueous layer, I think I understand that portion but how would it be applied to something like chloroform that's where I'm really getting confused.

Thank you

[Mitch]

No,no,no, you must review the concept of density better.

Whatever has the largest density will be at the bottom, and whatever has the smallest density will be on top.

[dexangeles]

the best way is to check the densities of each @ a CRC book

after that, you can deduce on which one is on top and which one is on the bottom

[jena]

Hi, let's see if i'm correct this time, so chloroform for example has a higher density than let's say water, then chloroform and dichloromethane will form on the bottom. Cyclohexane and heptane would form on the top because they are lighter than water. Water has a density of about 1.

Are these correct based off what you both have said

Thank you  

[Mitch]

You finally got it.  

[dexangeles]

i would'nt use the word "lighter" --- id rather say less dense or more dense
it would be wrong to say that 1000 liters of methane is lighter than 1 liter of water

but so far so good
just remember all you need to know are the densities then you're set
te hardest part is actually lookin up the densities on the CRC book

[jena]

Hi,

I have one more question dealing with this lab it states:

If toluene (density 0.87) were used to extract bromhydrin (density 2.41) from an aqueous solution:

By what test could you identify the nonaqueous layer?
My answer is by the pH test, and by that you can identify the nonaqeous layer

Is this a good answer, or should I look at it one more time.

Thank you

[movies]

The pH test might work, but only if the aqueous layer is basic or acidic.  If the aqueous layer is neutral, then the aqueous and organic layers would look the same on pH paper.

So assume that the top layer is the organic layer.  What would you expect would happen if you added one drop of water to the mixture?  What would you observe if the top layer was, indeed, the organic layer?  If the top layer turned out to be the aqueous layer, what would you observe then?

[jena]

Hi,

By adding water wouldn't it be insolulble in the organic layer, and soluble in the aqeous layer.  So adding water to your misture could act as another test to determine whether it is an organic or aqeous layer. Is this correct?

Thank You    

[Mitch]

Yes, but wht?

[jena]

Hi,

I guess Toulene would be the aqueous layer and bromhydrin would be the organic layer if that is that's what you mean.

Thank You  

[Mitch]

NO, because if you add water, you will see the aqueous layer get larger. While the organic layer stays the same volume.  

[jena]

Hi,

By why does it do that?


Thank You