How to choose a reduced or oxidated form in a redox

[Peppe]

Hi guys I'm studying about general chemistry in a physics class.
I've some exercices that I'm unable to solve, stuff like this:Copper can be solubilizated in water, oxidating in Cu++ form, reacting with HCrO4- in an acid environment realized by H2SO4. Write down the balanced reaction.my problem is to write (not to balance) an reduction/oxidation reaction.The copper is oxidating, so cromium or hydrogen have to reduce. I've thought about 3 different reaction.
So, in my proposal, the unbalanced reaction are:

Cu + HCrO4- -> Cu++ + Cr2O3 + H2O
Cu + HCrO4- -> Cu++ + CrO + H2O
Cu + HCrO4- -> CuCrO4 + H2

how to choose the correct one?
ciao!

 

[Borek]

Cr usually gets reduced to Cr³⁺ in such situations. You are probably right about copper chromate precipitation.

Please note: copper is not "oxidating", copper is "being oxidized" while chromium is being reduced.

 

[Peppe]

Thanks for the reply :) :) .

But how can i learn what usually a species does? :O