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Topic: Iron reactions with concentrated acids  (Read 18813 times)

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islamdiaa

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Iron reactions with concentrated acids
« on: December 09, 2009, 07:01:21 PM »
Iron reaction with Concentrated HNO3

Fe + HNO3  :rarrow: No reaction.  (Due to the passivity of iron)

Iron reaction with Concentrated H2SO4

Fe + H2SO4  :rarrow: FeSO4 + Fe2(SO4)3 + 4 SO2 + 8 H2O

I don't know why Iron reacts with conc. H2SO4 while doesn't react with conc. HNO3. And also I need to understand why and how each product was formed.

Thanks in advance!

Offline cliverlong

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Re: Iron reactions with concentrated acids
« Reply #1 on: December 10, 2009, 07:27:09 AM »
Iron reaction with Concentrated HNO3

Fe + HNO3  :rarrow: No reaction.  (Due to the passivity of iron)

I don't know why Iron reacts with conc. H2SO4 while doesn't react with conc. HNO3. And also I need to understand why and how each product was formed.

Try Google. I cut and paste to save you the effort.

Note concentration of nitric acid is relevant and nitric acid can act as both an acid and an oxidizing agent which leads to more complex products than, say, hydrochloric acid

http://en.wikipedia.org/wiki/Nitric_acid#Reactions_with_metals
http://en.wikipedia.org/wiki/Nitric_acid#Passivation

http://www.bookrags.com/research/nitric-acid-woc/
Gives
When nitric acid reacts with a metal the products that result are dependant upon the concentration of the acid used. This process is complicated by the fact that nitric acid acts as a strong oxidizing agent as well as an acid. Reactive metals will react with nitric acid to give the metal nitrate and hydrogen gas. Less reactive metals do not produce hydrogen at all. With dilute acid one of the principal products is nitrogen monoxide, while with concentrated acid it is nitrogen dioxide. In practical terms both reactions give the brown fumes normally associated with nitrogen dioxide, because the nitrogen monoxide rapidly reacts with the oxygen in the air to produce nitrogen dioxide. Treating metals (iron, chromium, aluminum, and calcium) with concentrated nitric acid can produce a protective oxide layer over the metal that halts further reactions.

http://chemicalland21.com/industrialchem/inorganic/NITRIC%20ACID.htm
Gives:
The action of nitric acid on a metal usually results in reduction of the acid (i.e., a decrease in the oxidation state of the nitrogen). The products of the reaction are determined by the concentration of nitric acid, the metal involved (i.e., its reactivity), and the temperature. In most cases, a mixture of nitrogen oxides, nitrates, and other reduction products is formed. Relatively unreactive metals such as copper, silver, and lead reduce concentrated nitric acid primarily to NO2. The reaction of dilute nitric acid with copper produces NO, while more reactive metals, such as zinc and iron, react with dilute nitric acid to yield N2O. When extremely dilute nitric acid is used, either nitrogen gas or the ammonium ion (NH4+) may be formed.

Quote
Iron reaction with Concentrated H2SO4

Fe + H2SO4  :rarrow: FeSO4 + Fe2(SO4)3 + 4 SO2 + 8 H2O

I don't know why Iron reacts with conc. H2SO4 while doesn't react with conc. HNO3. And also I need to understand why and how each product was formed.

Thanks in advance!
http://en.wikipedia.org/wiki/Sulfuric_acid#Other_reactions

Indicates concentrated sulphuric acid can act as an oxidizing agent

http://www.tutorvista.com/content/chemistry/chemistry-ii/sulphur/concentrated-acid.php (section b ii)

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Thanks in advance!
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islamdiaa

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Re: Iron reactions with concentrated acids
« Reply #2 on: December 10, 2009, 09:13:39 AM »
Thanks very much for you help.

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