A) which of the following reagents would oxidize cr to cr2 , but not fe to fe3 ?

The answer is Co2+  This is the reagent that would oxidize Cr to Cr2 , but not Fe to Fe3. A metal that lies between Cr and Sn is Cobalt. In order for it to oxidize Cr, it has to be Co+2 (Cobalt cation).

Ions gain or lose electrons

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