An excess of copper(II) oxide is added to dilute sulfuric acid to make crystals of hydrated copper(II) sulfate.

The processes listed may be used to obtain crystals of hydrated copper(II) sulfate.

  1. concentrate the resulting solution
  2. filter
  3. heat the crystals
  4. wash the crystals

Which processes are needed and in which order?

A 1, 2, 3 and 4
B 1,2, 4 and 3
C 2, 1, 2 and 3
D 2, 1, 2 and 4

I know the correct answer is D. I understand that the solution is first filtered to remove excess copper(II) oxide. Then copper(II) sulfate is saturated by adding excess of it. Then filtered again to remove excess. The last step is wash the crystal. Isn't it needed to heat the solution to get crystal? Also is my understanding so far correct?

  • 2
    $\begingroup$ There is no mandatory requirement to heat the solution. Then again, how exactly were you going to concentrate it? $\endgroup$ Commented Mar 27, 2019 at 9:09
  • $\begingroup$ @IvanNeretin Been trying to understand the answer for quite some time now. And these are just some assumption I made $\endgroup$
    – Jamy
    Commented Mar 27, 2019 at 9:16
  • $\begingroup$ Yes, your understanding is correct. As for the heating, see my previous comment. $\endgroup$ Commented Mar 27, 2019 at 9:31

1 Answer 1


Step 2) You would filter the solution as you would have added excess copper oxide to ensure all acid has reacted. Step 1) Then you would concentrate/saturate (saturated solution is a solution containing the maximum concentration of a solute dissolved in a solvent at a specific temperature) the solution by heating, Step 2) You would leave the solution to cool and crystallise (form crystals), and so there would be crystals at the bottom and so you would need to filter to collect the crystals Step 4) You wash the crystals with cold distilled water to remove impurities. distilled water is purified (no salts, minerals etc) water and lacks ions. This ensures that it will not solubilize the crystals and plus you are only using a tiny amount and not submerging the crystals in distilled water, right after that, you dry the crystals in between filter paper to remove any of the little remaining distilled water


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