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I am designing a batch reaction between iron ingots and dilute nitric acid. Since there will no doubt be NOx given out, I am trying to see if it is feasible to blow in Oxygen/compressed air into the reactor to transfer NO into NO2.

However, there pops up a question that whether this reaction generates H2 or not? If this is the case, then I have to design bubbling tanks with H2O2 after the reactor, instead of just blow in O2 into the reactor.

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  • $\begingroup$ Another problem due to nitric acid is the protective layer of $\ce{Fe3O4}$ that nitric acid solutions produce on the surface of iron ingots This layer prevent any further reaction with iron. This phenomena is often called passivation. It is avoided by adding some other metal like copper in contact with the ingot. $\endgroup$
    – Maurice
    Commented Oct 28 at 11:53
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    $\begingroup$ @Maurice Passivation should happen when iron reacts with concentrated HNO3, but is it the case also for diluted HNO3, it also happens? $\endgroup$
    – Bobet AJIA Louison
    Commented Oct 29 at 6:04

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Did a test using 5% HNO3 to attack iron ingots in a beaker, and found H2, in a concentration of a few hundreds of ppm. Problem solved.

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  • $\begingroup$ Your are giving an empirical answer but you are not justifying or explaining your observations with a chemical justification. No need for doing an experiment. You could have answered it using the standard electrode potentials of the reaction. $\endgroup$
    – PAEP
    Commented Oct 31 at 13:40
  • $\begingroup$ I would imprivevthe answer by (1) describing the rechniques you used to samplecand measure the fas evolution, (2) making the potenrial comparison noted previously. It's actually very hard to displace hydrogen from nitric acid. $\endgroup$
    – Oscar Lanzi
    Commented Nov 1 at 13:03

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