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How can I make $\ce{Cu2O}$ from copper?

I am seeing if electrolysis is a good route (in the context of kitchen style chemistry) to cuprous oxide, instead of the traditional heating copper and removing the cupric oxide, etc.

With Epsom salt electrolyte, it is very easy to make copper II hydroxide (cloudy ammonia soluble, according to the wiki). This can be heated to $\ce{CuO}$ easily enough, but I have no idea if this can be reduced.

Can $\ce{CuO}$ be reduced easily? Or is there a simple way to produce (from copper) a copper (I) salt, from which a precipitate of $\ce{Cu2O}$ may be formed? What reducing agents could be used?

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  • $\begingroup$ using the more sensible electrolyte NaOH gives better results and ammonia is indeed a good solvent - the sky blue hydroxide forms a deep blue solution like copper sulfate. Now the challenge remains to reduce this solution, as with Benedict's reagent or Fehling's solution. Any thoughts? $\endgroup$ Apr 22, 2014 at 10:54
  • $\begingroup$ i bought glucose and hesitantly boiled the ammonia solution after adding an excess - it create a very fine orange suspension. i have no idea how to cause it to settle though, as heating will produce the black oxide (as the last water evaporates, possibly?). $\endgroup$ Apr 23, 2014 at 9:35
  • $\begingroup$ Copper (I) has a half-filled orbital, so transforming this would be relatively easy, $\endgroup$ May 22, 2017 at 9:10
  • $\begingroup$ Six years after the original post, I wanted to do the same thing (get some Cu2O), and Benedict's reagent seems to be the way to go, as far as kitchen chemistry is concerned. I made 100 mL Benedict's according to wikipedia (only I used citric acid and washing soda, as I did not have trisodium citrate at hand, but the math is simple...). It's not a high-throughput technique, only 2 grams of copper sulfate (sorry, my kitchen scale only has 1 gram resolution), I reduced it with about 2 grams of glucose (smarties candy) by boiling in microwave oven. All of the Cu 2+ gets reduced to Cu2O. The brick- $\endgroup$
    – Zdenek
    May 9, 2020 at 5:46

1 Answer 1

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There are several ways to make copper(I) oxide from copper:-

  1. Heat it

$$\ce{4Cu + O2 ->[\Delta] 2Cu2O}$$

Copper react with oxygen to produce copper(I) oxide. This reaction takes place at a temperature of over 200°C.

  1. Heat it with nitrous or nitric oxide

$$\ce{2Cu + N2O->[\Delta] Cu2O + N2}$$ $$\ce{4Cu + 2NO->[\Delta] 2Cu2O + N2}$$

Copper react with nitrous and nitric oxide to produce copper(I) oxide and nitrogen. Both reaction takes place at a temperature of 500-600°C.

  1. Heat it with copper(II) oxide

$$\ce{Cu + CuO->[\Delta] Cu2O}$$

Copper react with copper oxide to produce copper(I) oxide. This reaction takes place at a temperature of 1000-1200°C.

  1. If you made copper (II) oxide, just heat it

$$\ce{4CuO ->[\Delta] 2Cu2O + O2}$$

The thermal decomposition of copper oxide to produce copper(I) oxide and oxygen. This reaction takes place at a temperature of 1026-1100°C.

Since you are doing this at home, method 2,3,4 cannot be used as it requires laboratory grade heater but method 1 can be used since it require 200°C which is achievable.

But the best method(according to the comment) I would recommend is the Fehling's test. All you need is Fehling's solution and glucose which can be purchased from sigma-aldrich at affordable price.

$$\ce{RCHO + (2Cu^2+ + 5OH^{-})->Cu2O + RCOO^- + 3H2O}$$

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