IGCSE Edexcel - Chemistry Paper 2H

Yeh..thats the one when you talk about adding HCl in excess to CuO powder..which makes Cu2SO4 after filtration! then evapourate all the water to get the crystals....Isnt it?

basically react the chemicals

filter

heat the solution gently, for evaporation + to make the soln more concentrated

wash

dry (i forgot this bit grr!)

Leave to cool, crystals form

ethanol --> ethene + water

i found one source saying sulphuric or phosphoirc acid can be used, with 170 degrees celcius: http://www.chemguide.co.uk/mechanisms/elim/dhethanol.html


and another with alluminum oxide:http://www.gcsescience.com/o44.htm

I dont think you have to dry of this one...i mean the crystals are hydrated copper sulphate...

Dry crystals were needed – surely this means that there should be no water of crystallisation.

IE. Heat the water out gently, but leaving it to naturally evaporate won’t produce dry crystals.

If ye wish for crystals, ye must have water of CRYSTALLISATION. Therefore, (as we did a lot of these is class), dry means exactly that, dry. So you can dry it with absorban material, such as blotting paper. This ensures that there is no water left outside of the crystal lattice.