When treated with nitric acid which of the following liberates hydrogen? (a) zinc □(b) copper (c

step 1 Question is when treated with nitric acid which of the following liberates hydrogen. So we are g

When treated with nitric acid which of the following...

Key Concepts

Oxidizing Acid Properties

Nitric acid is classified as a strong oxidizing acid, which means that in reactions with metals it not only protonates the metal but also oxidizes it. Unlike typical mineral acids like hydrochloric acid, nitric acid’s oxidizing power prevents the simple evolution of hydrogen gas by converting the nascent hydrogen into water as it reduces nitrate ions to nitrogen oxides.

Hydrogen Evolution Reaction

In many acid-metal reactions, especially with non?oxidizing acids, hydrogen gas is released as the metal reduces protons to hydrogen. However, when an oxidizing acid such as nitric acid is used, the usual hydrogen evolution is inhibited because the reactive intermediates are rapidly oxidized, thus preventing free hydrogen gas from being observed.

Redox Reaction Mechanism

The interaction between a metal and nitric acid proceeds through a redox mechanism where the metal is oxidized to its corresponding salt (nitrate) and the nitric acid is reduced, typically forming various nitrogen oxides (like NO or NO2). This redox pathway bypasses the intermediate formation of molecular hydrogen, altering the expected outcome compared to reactions with less oxidizing acids.

Metal Reactivity Considerations

Although metal reactivity often predicts the evolution of hydrogen gas in acid reactions (as seen in the reactivity series with acids like HCl), the specific reaction conditions with nitric acid deviate from this norm. The oxidizing nature of nitric acid modifies the typical behavior of metals, meaning that even metals that are normally active in hydrogen displacement reactions do not liberate hydrogen when reacting with nitric acid.

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