In the acidic medium Cl
2 can be formed as a result of the comproportionation reaction:
HClO + Cl
- + H
+ Cl
2 + H
2O
Chloride is present in the regular bleach, and it can also be there due to the partial decomposition of NaClO to NaCl and oxygen
In the acidic solutions the formation of chlorine gas is favoured. The reverse reaction, the disproportionation/dissolution of chlorine is favoured in the basic medium.
No, the nitrogen in HNO
3 is already in the highest oxidation state, it can only be reduced.
Another question: can you tell the difference between Cl
2 and ClO
2? They are both yellowing-green gases. Think about the oxidation of the hypochlorite to chlorine dioxide by concentrated nitric acid. I am not sure if this is possible because the hypochlorite itself is a very strong oxidizing agent, the strongest in the ClOx series.. Find the potential of this reaction at low pH to see if it is (at least) possible thermodynamically..