1.

Explain the reaction of metals with nitric acid.

Answer»

Solution :The reaction of metals with nitric acid are explained in 3 steps as follows:
Primary reaction : Metal nitrate is formed with the RELEASE of nascent hydrogen
`M+HNO_(3)rarr MnO_(3)+(H)`
SECONDARY reaction : Nascent hydrogen PRODUCES the reduction products of nitric acid.
`HNO_(3)+2H rarr underset("Nitrous acid")(HNO_(2)+H_(2)O)`
`HNO_(3)+6Hrarr underset("Hydroxylamine")(NH_(2)OG+2H_(2)O)`
`HNO_(3)+8Hrarr underset("Ammonia")(NH_(3))+3H_(2)O`
`2HNO_(3)+8H rarr underset("Hypop nitrous acid")(H_(2)N_(2)O_(2))+4H_(2)O`
Tertiary reaction : The secondary products either decompose or react to give final products
`underset("Nitrous acid")(3HNO_(2))rarr underset("Nitric acid")(HNO_(3))+underset("Nitric oxide")(2NO+H_(2)O)`
Tertiary reacton : The secondary products either decompose or react to give finalproducts
`underset("Nitrous acid")(3HNO_(2))rarr underset("Nitric acid")(HNO_(3))+underset("Nitric oxide")(2NO)+H_(2)O`
`undeerset("Nitrous acid")(2HNO_(2))rarr underset("Dinitrogentrioxide")(N_(2)O_(3))+H_(2)O`
`underset("Hypo nitrous acid")(H_(2)N_(2)O_(2))rarr underset("Nitrouc oxide")`
For examples :
Copper reacts with nitric acid in the following manner
`3Cu+6HNO_(3)rarr 3Cu(NO_(3))_(2)+6(H)`
`6(H)+3HNO_(3)rarr 3HNO_(2)+3H_(2)O`
`3HNO_(2)rarr HNO_(3)+2NO+H_(2)O`
Overall reaction
`3Cu+8HNO_(3)rarr 3Cu(NO_(3))_(2)+2NO+4H_(2)O`
The concentrated acid has a tendency to FORM nitrogen dioxide
`Cu+4HNO_(3)rarr Cu(NO_(3))_(2)+2NO_(2)+2H_(2)O`


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