[paulE]

Hello
I´ve checked the reaction between HNO3 and NaClO. It produces a lot of Cl2 gas.
So NaClO seems the oxidizer here.I think this is logical, as oxidation potential for ClO- is bigger than NO3- , both in acid conditions.
Question is ,if nitrogen in HNO3 is in its upper oxidation valence (+5)...how is going to be oxidized?
What is the final nitrogenated product?
I think there must be some intermediate products, but i don´t know how to formulate this reaction.
Thank you
 

[Borek]

Have you tried to assign oxidation numbers to chlorine in Cl₂ and ClO^-?

[unsu]

Hello
I´ve checked the reaction between HNO3 and NaClO. It produces a lot of Cl2 gas.
So NaClO seems the oxidizer here.

Could you please provide some more details about this reaction?
Did you see it somewhere or did you do this experiment yourself?
What exactly did you observe?
What was the concentration of nitric acid?
Did you use pure NaClO or a regular bleach, which may contain some dissolved chlorine, NaClO and NaCl?
Are you sure it was Cl₂ and not NO₂?

[paulE]

Yes, I´ve tested this reaction myself.HNO3 conc was standard 63%. NaClO was in excess (bleach).There is a clear production of gas bubbles.
I'm sure released gas is Cl2 because it´s green and smells clearly as Cl2. NO2 would be brown-reddish...I known Cl2 smell quite well...

[paulE]

Yes, I´ve tested this reaction myself.HNO3 conc was standard 63%. NaClO was in excess (bleach).There is a clear production of gas bubbles.
I'm sure released gas is Cl2 because it´s green and smells clearly as Cl2. NO2 would be brown-reddish...I known Cl2 smell quite well...
About the reaction

2ClO- + 4H+ + 2e -> Cl2 + 2H2O

but my doubt is what must nitrogen do to release those two electrons,as it is already in +5 oxidation number. Don´t know what is the other semi redox reaction for nitrogen.

[unsu]

In the acidic medium Cl₂ can be formed as a result of the comproportionation reaction:
HClO + Cl^- + H⁺  Cl₂ + H₂O
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 HNO₃ is already in the highest oxidation state, it can only be reduced.

Another question: can you tell the difference between Cl₂ and ClO₂? 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..

[unsu]

I just wanted to add that when you react the bleaching powder (chlorinated lime, CaOCl₂ or Ca(OCl)₂*CaCl₂) with hydrochloric or sulfuric acid, the chlorine gas is formed:
CaOCl₂ + 2HCl  = CaCl₂ + Cl₂ + H₂O
CaOCl₂ + H₂SO₄ = CaSO₄ + Cl₂ + H₂O

This might help. I did these experiments in my first year inorganic labs.

[paulE]

Thanks for your answer.
I´ve checked there is no acid reaction when i sink an indicator paper.Also, I´ve added sodium bicarbonate NaHCO3 and i see no CO2 release, so there is no HNO3 (not even H+) in the liquid.

About HClO + Cl- + H+  -> Cl2 + H2O I think there is too much Cl2 production that needs a lot of Cl- ions in solution.Maybe too much for being due to dissociation on NaClO, but I´m not sure.

About the ClO2, i´m not sure if i can write the reaction...What would be the final oxidation number of nitrogen? (consistent with the fact there is no NO/NO2 production)

I´ll think about your last message,about reaction of HCl and H2SO4 with CaOCl2 and see is something similar with HNO3 could be true.

[paulE]

May be as easy as this?

NaClO + NaCl + 2HNO3 -> Cl2 + H2O + 2NaNO3

I´ve checked there is Cl- ion in that bleach with a drop of AgNO3...
How could i get rid of that NaCl to check what happens then? Also, if that´s true, after cristalization of the result, i´m supposed to obtain pure NaNO3. that would be a nice confirmation.

[unsu]

Sodium hypochlorite bleach is prepared by passing Cl₂ through aqueous NaOH. There must be equimolar amounts of NaClO and NaCl present. The equilibrium reaction takes place:
ClO^- + H₂O  HClO + OH^-

When you add acid, the equilibrium shifts to the right:
H⁺ + OH^- = H₂O, and
ClO^- + H⁺ = HClO (HClO = weak acid)
or simply:
NaClO + HNO3  HClO + NaNO₃

The mixture of HClO and Cl^- is not stable with respect to comproportionation in the acidic solution:
HClO + NaCl + HNO₃= Cl₂ + NaNO₃ + H₂O

Try the same reaction with sulfuric acid
Cheers

[paulE]

February 14
I let the solution to dry. Washed wih alcohol those nice white crystals.Dissolved in water, and tested with AgNO3...and no signs of Cl ions. I added some H2SO4 to a small amount of crystals, put a small copper piece and ...ots of NO/NO2 gas delivered...So, its NaNO3 as expected.

[Arkcon]

Good job, confirming the result with an experiment.  Lots of people won't take the time for that.