Chromium, Cr, is a transition metal. It is obtained from its oxide by the reaction Cr₂O₃ + 2Al → Al₂O₃ + 2Cr.

1. aWhat is the oxidation state of chromium in Cr₂O₃? [1]
2. bWhat is the oxidation state of aluminium in Al₂O₃? [1]
3. cState the reducing agent in the reaction. [1]
4. dDescribe a test to confirm that aluminium is a reducing agent. [2]

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