Redox interconversions of chromium ions

22. understand, in terms of the relevant $E^{\ominus}$ values, that the dichromate(VI) ion, Cr₂O₇²⁻:

i can be reduced to Cr³⁺ and Cr²⁺ ions using zinc in acidic conditions

ii can be produced by the oxidation of Cr³⁺ ions using hydrogen peroxide in alkaline conditions (followed by acidification)