Decide whether or not each metal dissolves in 1 M HNO3. For those metals that do

Question

Decide whether or not each metal dissolves in 1 M HNO3. For those metals that do dissolve, write a balanced redox reaction showing what happens when the metal dissolves.

Part A

Co

Express your answer as a chemical equation. Enter noreaction if there is no reaction. Identify all of the phases in your answer.

Decide whether or not each metal dissolves in 1 M HNO3. For those metals that do dissolve, write a balanced redox reaction showing what happens when the metal dissolves.

Part A

Co

Express your answer as a chemical equation. Enter noreaction if there is no reaction. Identify all of the phases in your answer.

Explanation / Answer

Nitric acid reacts with most metals but the details depend on the concentration of the acid and the nature of the metal. Dilute nitric acid behaves as a typical acid in its reaction with most metals. Magnesium, manganese and zinc liberate H2. Others give the nitrogen oxides.

The reactions are as following

                 Mg + 2 HNO3 = Mg(NO3)2 + H2

                 Mn + 2 HNO3 = Mn(NO3)2 + H2

                 3 Cu + 8 HNO3 = 3 Cu(NO3)2 + 2 NO + 4 H2O

Although chromium (Cr), iron (Fe), and aluminium (Al) readily dissolve in dilute nitric acid, the concentrated acid forms a metal oxide layer that protects the bulk of the metal from further oxidation. The formation of this protective layer is called passivation. Typical passivation concentrations range from 20–50% by volume. Metals that are passivated by concentrated nitric acid are iron, cobalt, chromium,nickel, and aluminium.

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