Question

How is cobalt metal oxidized by hydrochloric acid?

Answer 1

`Co(s) + 2HCl(aq) rarr CoCl_2(aq) + H_2(g)uarr`

Explanation:

I have not got a table of redox potentials in front of me, so I cannot tell you if the reaction is feasible (I think it just is!). The oxidizing agent is the species whose oxidation number DECREASES, and thus it is `H^+`, the hydronium ion, and we can write is reduction reaction as follows...

`H^+ + e^(-) rarr 1/2H_2(g)`..........

Protium ion is reduced, and the electron is presumed to come from somewhere, i.e. from the metal, thereby oxidizing it......

`Co(s) rarr Co^(2+) + 2e^(-)`.......