Question

A metal which reacts with very dilute Nitric acid is:

• A. Calcium
• B. Magnesium
• C. Copper
• D. Zinc

Answer 1

The correct option is B

Magnesium

Explanation for the correct option:

B: Magnesium

1. Dilute Nitric acid when reacted with metals does not give Hydrogen gas except for Magnesium (Mg) and Manganese (Mn).
2. It works as a powerful oxidising agent, which gives nascent oxygen.
3. The nascent oxygen oxidises the liberated Hydrogen to form water.
4. When Magnesium reacts with very dilute Nitric acid then it produces Magnesium nitrate and Hydrogen gas.
5. Due to dilution the oxidising action of Nitric acid will get reduced.
6. The chemical reaction occurs as follows: $\underset{\left(\mathrm{Magnesium}\right)}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{(\mathrm{Nitric}\mathrm{acid})}{2{\mathrm{HNO}}_3(dil.)}\to \underset{(\mathrm{Magnesium}\mathrm{nitrate})}{\mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)}+{\mathrm{H}}_2\left(\mathrm{g}\right)$
7. Therefore, the correct option is B. Magnesium reacts with very dilute Nitric acid to form Magnesium nitrate and hydrogen gas.

Explanation for the incorrect option:

A: Calcium

1. Calcium does not react with Nitric acid in its dilute form.
2. Calcium reacts with Nitric acid in its concentrated form.
3. The chemical reaction that occurs with Calcium is as follows:
   $\mathrm{Ca}\left(\mathrm{s}\right)+\underset{(\mathrm{Nitric}\mathrm{acid})}{4{\mathrm{HNO}}_3(conc.)}\to 4\underset{(\mathrm{Calcium}\mathrm{nitrate})}{\mathrm{Ca}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)}+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+2N{O}_2\left(\mathrm{g}\right)$
4. Hence, option A is incorrect.

C: Copper

1. Copper reacts with Nitric acid in its concentrated form.
2. The chemical reaction occurs between Copper and Nitric acid to liberate the oxidised product.
3. When Copper reacts with Nitric acid it forms Copper nitrate, Water, and Nitrogen dioxide.
4. The chemical reaction occurs as follows:
5. $\mathrm{Cu}\left(\mathrm{s}\right)+\underset{(\mathrm{Nitric}\mathrm{acid})}{2{\mathrm{HNO}}_3(conc.)}\to \underset{(\mathrm{Copper}\mathrm{nitrate})}{\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)}+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+2{\mathrm{NO}}_2\left(\mathrm{g}\right)$
6. Hence, option C is incorrect.

D: Zinc

1. Zinc reacts with Nitric acid in its concentrated form to liberate Nitrogen dioxide.
2. Zinc reacts with Nitric acid to form Zinc nitrate, water, and Nitrogen dioxide.
3. The chemical reaction occurs as follows:
   $\mathrm{Zn}\left(\mathrm{s}\right)+\underset{(\mathrm{Nitric}\mathrm{acid})}{4{\mathrm{HNO}}_3(conc.)}\to \underset{(\mathrm{Zinc}\mathrm{nitrate})}{\mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)}+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+2N{O}_2\left(\mathrm{g}\right)$
4. Hence, option D is incorrect.