Question

Why dont metals react with HNO3 to liberate hydrogen except Mn and Mg ??

Answer fast plz !!
The best one will be marked brainliest !!

Answer 1

Heya
Here's your answer !!

Generally when metals are treated with mineral acids hydrogen gas is liberated but when metals (except Mn and Mg) are treated with HNO3 , hydrogen is not liberated.

This is because Nitric acid ( HNO3 ) is a powerful oxidising agent , and the oxygen formed due to its decomposition oxidises the hydrogen to give water thus defeating the purpose of the reaction .

3Zn + 8HNO3 -----> 3Zn(NO3)2 + 4H20 + 2NO (g) .

Even Magnesium and manganese react with very dilute nitric acid ( 1% nitric acid ) to liberate hydrogen . The oxidising action of the acid is much reduced due to its over dilution .

Mg + 2HNO3 ----> Mg(NO3)2 + H2 (g) .

Hope it helps !!

Answer 2

Dear folk!!

Any metal above hydrogen in the activity series will react with dilute HNO3 to produce hydrogen gas and the oxidized form of the metal in solution. If the HNO3 is very concentrated (above 8 or 10 molar), then NO gas is produced. NO gas quickly oxidizes in air to produce the characteristic reddish brown NO2 gas that we observe when copper metal reacts with nitric acid. Hope this helps!!