Ethanol - salt precipitation

jsmith613

1. The problem statement, all variables and given/known data


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
2. Relevant equations


3. 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

http://www.creative-chemistry.org.uk...s/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

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

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

Sounds good to me.