bob800 - 16-8-2010 at 19:00
I made some copper(II) hydroxide by precipitating it from 8g NaOH and 25g CuSO4. I filtered it (gravitationally) and let it sit for a day (in the
filter paper), and when I came back much of it had turned black, I think because of copper(II) oxide contamination. On Wikipedia it says that moist
copper(II) hydroxide will slowly turn into CuO until its dry, so I think thats what happened.
Anyway, my question is: Is there any way to turn the copper(II) oxide back into copper(II) hydroxide?
woelen - 16-8-2010 at 22:27
Redissolve the solid in a little dilute sulphuric acid and then add NaOH again. But now do this while the liquid is very cold and work with more
dilute solutions, such that no local hot spots can be formed. Filter the solid and rinse with cold distilled water. Then allow to dry in a cool place.
In this way you'll get reasonably pure Cu(OH)2, but not really pure. Cu(OH)2 also absorbs CO2 from air, making a basic carbonate, so your material
will be contaminated with some carbonate.
Random - 16-8-2010 at 23:51
If you want to use copper hydroxide to make more copper compounds, I suggest you making copper carbonate with Na2CO3 and CuSO4.