What Is the Role of Ethanol in Precipitating Salts?

[jsmith613]

Homework Statement

what is the purpose of adding ethanol in step 5 in the following description?

http://www.creative-chemistry.org.uk...s/N-ch5-08.pdf

Homework Equations

The Attempt at a Solution

Does adding ethanol make the liquid phase (which is now a homogenous mixture) less polar because ethanol is slighly hydrophobic hence the salt is less soluble so precipitates out?

 

[Borek]

Link is broken.

But your explanation is more or less what could be expected.

 

[jsmith613]

Link is broken.

But your explanation is more or less what could be expected.

http://www.creative-chemistry.org.uk/alevel/module5/documents/N-ch5-08.pdf

 

[Borek]

I don't think calling ethanol hydrophobic is the best approach. It has a lower dielectric constant and because of its size it is not as effective at solvation, so it doesn't isolate ions as effectively as water does.

 

[jsmith613]

I don't think calling ethanol hydrophobic is the best approach. It has a lower dielectric constant and because of its size it is not as effective at solvation, so it doesn't isolate ions as effectively as water does.

would it please be possible then to give me an A2 level answer (i don't know about dielectric constant) that would gain 1 or 2 marks?

thanks

 

[jsmith613]

I don't think calling ethanol hydrophobic is the best approach. It has a lower dielectric constant and because of its size it is not as effective at solvation, so it doesn't isolate ions as effectively as water does.

would the following be better:

"the homogeneous mixture of ethanol and water is less polar that water alone so the salt is less soluble and hence precipitates out

 

[Borek]

the homogeneous mixture of ethanol and water is less polar that water alone so the salt is less soluble and hence precipitates out

Sounds good to me.