Preparation of a chromium(II) ethanoate complex

Zinc metal is used to reduce an acidified solution of sodium dichromate from its original orange 6+ oxidation state, through the green 3+ state and then to the final blue 2+ state. Use standard electrode potentials to check that these reactions are feasible and check your conclusions using the link below.

We use the hydrogen gas generated by the zinc-acid reaction to push the blue, hexaquo chromium(II) solution into the sodium ethanoate solution in order to generate our product. Although it works just as well if you carefully dismantle your apparatus and quickly pour your blue chromium(II) solution directly into the sodium ethanoate solution. At the end of the experiment we compare the chromium(II) ethanoate complex with the chromium(II) aquo complex. Try to explain what is happening here.

Video - preparation of a complex

Electrode potential predictions and observations