How could ethanol and acetone speed up water evaporation?

[Red7]

In a chem lab we had an unknown copper compound in water, we used Magnesium to displace the copper and added HCl to speed things up. The copper fell to the bottom of the beaker and we then poured the solution through filter paper to catch and weigh the copper. Once the copper was in the filter paper we had to rinse it in ethanol and acetone before putting it in the oven to evaporate everything aside from the copper(II) and the paper.

 

Can someone please explain the purpose of the ethanol and acetone? Thanks a ton.

 

red7

[insane_alien]

likely just to rinse off the majority of the remaining solution so the copper is clean when it comes out. the lower heat of evapouration and greater vapour pressure of acetone and ethanol would also allow quicker drying.

[Justonium]

I have done that same lab in my school, and we rinsed the filtered copper with acetone because copper reacts with air when it is wet to produce copper carbonate, which will make the sample turn green and weigh more. To prevent this reaction from happening while the copper was drying, we used acetone to rinse the water out. After the acetone drains off, the liquid which is wetting the copper is mostly acetone, which will not react. Acetone also evaporates faster than water, making the drying go faster, but this is not the main purpose of rinsing with acetone; water will still dry in a warm oven. If you're wondering why the copper would react, the copper reduced from the solution has a very porous surface, and reacts with air and water much more quickly than copper with a smooth surface (like a penny) would. I once left some freshly precipitated wet copper out in the air and it was already completely corroded less than an hour later.

[Red7]

Thanks a lot guys, I appreciate it.

 

Red7

[Horza2002]

Both the above are true. Ehanol and acetone will also interfere with waters H-bond system making it less efficient. With that happening, water will more easily evapourate