Comment on the reactions of dihydrogen with (i) chlorine, (ii) sodium, and (iii) copper(II) oxide ?

When we look at the reactions of dihydrogen (H₂) with different substances, we can see a variety of chemical behaviors that highlight the reactivity of hydrogen in different contexts. Let's break down the reactions with chlorine, sodium, and copper(II) oxide one by one.

Reaction with Chlorine

Dihydrogen reacts vigorously with chlorine gas (Cl₂) to form hydrogen chloride (HCl). This reaction is highly exothermic, meaning it releases a significant amount of energy, often in the form of heat and light. The balanced chemical equation for this reaction is:

• H₂(g) + Cl₂(g) → 2 HCl(g)

This reaction can be initiated by light or heat, which provides the energy needed to break the Cl-Cl bond in the chlorine molecule. Once the reaction starts, it can proceed rapidly, producing hydrogen chloride gas, which is corrosive and can form hydrochloric acid when dissolved in water. The bright flame produced during the reaction is a visual indicator of the energy released.

Interaction with Sodium

When dihydrogen comes into contact with sodium (Na), a highly reactive alkali metal, the reaction is also vigorous but occurs under different conditions. Sodium reacts with dihydrogen to form sodium hydride (NaH). The reaction can be represented as:

• 2 Na(s) + H₂(g) → 2 NaH(s)

This reaction typically requires heat to initiate, as sodium must be in a molten state for the reaction to proceed effectively. Sodium hydride is a white solid that is used in various applications, including as a strong base in organic synthesis. The formation of sodium hydride illustrates how dihydrogen can act as a reducing agent, facilitating the transfer of hydrogen to the sodium.

Reaction with Copper(II) Oxide

In the case of copper(II) oxide (CuO), dihydrogen serves as a reducing agent. When dihydrogen is passed over heated copper(II) oxide, it reduces the copper(II) oxide to copper metal while itself being oxidized to water. The balanced equation for this reaction is:

• CuO(s) + H₂(g) → Cu(s) + H₂O(g)

This reaction is significant in metallurgy, particularly in the extraction of metals from their ores. The heat required for this reaction can be provided by a furnace, and the result is the production of elemental copper, which can be collected as a solid. This demonstrates hydrogen's role not only as a fuel but also as a reducing agent in chemical processes.

Summary of Reactions

To summarize, dihydrogen exhibits different reactivity depending on the substance it interacts with:

• With chlorine, it forms hydrogen chloride in a highly exothermic reaction.
• With sodium, it produces sodium hydride, showcasing its ability to reduce metals.
• With copper(II) oxide, it reduces the oxide to copper while being oxidized to water.

These reactions highlight the versatility of dihydrogen as a reactant in various chemical processes, illustrating its importance in both organic and inorganic chemistry.