Question

Which property of hydrogen is shown by the following reactions? (i) \(\mathrm{Fe}_{3} \mathrm{O}_{4}+4 \mathrm{H}_{2} \rightarrow 3 \mathrm{Fe}+4 \mathrm{H}_{2} \mathrm{O}\) (ii) \(\mathrm{CO}+\mathrm{H}_{2} \stackrel{\mathrm{ZnO},}{\mathrm{Cr}_{2} \mathrm{O}_{3}} \mathrm{CH}_{3} \mathrm{OH}\) (a) Reducing character (b) Oxidising character (c) Combustibility (d) High reactivity

Short answer

The property of hydrogen shown by both reactions is (a) Reducing character.

Step-by-step solution

Analyze the first reaction

Identify the changes in oxidation states of the elements in the first reaction. In the reaction \(\mathrm{Fe}_{3} \mathrm{O}_{4}+4 \mathrm{H}_{2} \rightarrow 3 \mathrm{Fe}+4 \mathrm{H}_{2} \mathrm{O}\), iron (Fe) is reduced from an oxide form to elemental iron, and hydrogen (H) is oxidized to water (H2O).

Analyze the second reaction

Examine the changes in the second reaction using its catalysts as an indication of the type of reaction. With \(\mathrm{CO}+\mathrm{H}_{2} \stackrel{\mathrm{ZnO}, \mathrm{Cr}_{2} \mathrm{O}_{3}}{\rightarrow} \mathrm{CH}_{3} \mathrm{OH}\), hydrogen (H) combines with carbon monoxide (CO) to form methanol (CH3OH) without any oxidation or reduction of hydrogen.

Determine the property of hydrogen

Based on the reactions where hydrogen causes other substances to gain electrons (reduce), we can conclude the property of hydrogen being demonstrated.

Key concepts

Reducing Character of Hydrogen

Understanding the reducing character of hydrogen is essential in the realm of chemistry. Essentially, a reducing agent is something that donates electrons to another substance in a chemical reaction, thereby reducing the other substance. Hydrogen, with its ability to do so, is often employed as a reducing agent.

In the exercise, the equation (i) \(\mathrm{Fe}_{3}\mathrm{O}_{4} + 4\mathrm{H}_{2} \rightarrow 3\mathrm{Fe} + 4\mathrm{H}_{2}\mathrm{O}\) perfectly illustrates this concept. During this reaction, hydrogen molecules donate electrons to iron oxide (\(\mathrm{Fe}_{3}\mathrm{O}_{4}\)), which results in the iron atoms being reduced from their oxide form and transitioning to a purer iron state. Meanwhile, the hydrogen itself becomes water (\(\mathrm{H}_{2}\mathrm{O}\)), displaying a clear shift from a neutral molecule to an oxidized one.

From the given exercise, it’s evident that hydrogen's ability to donate electrons determines its reducing character. This reducing power can be manipulated in various chemical processes, including metallurgy for extracting metals from their ores or in organic chemistry to reduce double bonds in organic compounds.

Chemical Reactions of Hydrogen

Hydrogen is a versatile element when it comes to its participation in chemical reactions. Its small size and high electronegativity allow it to react in numerous ways, often determined by the conditions of the reaction and the nature of the other reactants.

In the reaction (ii) \(\mathrm{CO} + \mathrm{H}_{2} \stackrel{\mathrm{ZnO}, \mathrm{Cr}_{2}\mathrm{O}_{3}}{\rightarrow} \mathrm{CH}_{3}\mathrm{OH}\), we observe that under the influence of catalysts (Zinc Oxide and Chromium(III) oxide), hydrogen combines with carbon monoxide to produce methanol (\(\mathrm{CH}_{3}\mathrm{OH}\)). This synthesis showcases hydrogen's reactivity and speaks to its wide use in industry, particularly in the synthesis of alcohols which are significant as solvents, fuels, and intermediates in various chemical syntheses.

The capability of hydrogen to engage in both reductive and synthetic chemical reactions amplifies its role as an indispensable player in the world of chemistry.

Hydrogen in Redox Reactions

A redox (reduction-oxidation) reaction involves the movement of electrons between two substances. Hydrogen's role in these reactions is of immense importance, often shifting between being an oxidizing agent and a reducing agent depending on the context of the reaction.

For instance, in the given solution step analyzation, hydrogen starts in a neutral form as \(\mathrm{H}_{2}\) and ends up combined with oxygen in water, showing a loss of electrons, which characterizes oxidation. The iron in iron (III) oxide undergoes reduction as it gains electrons. This interplay highlights hydrogen's dynamic nature in redox reactions.

Applying the Concept to Hydrogen's Reductive Role

In the reaction, hydrogen fulfills the reducing role, demonstrating the broader principle that in redox reactions, elements or molecules can serve either as reducers or oxidizers, dictated by their respective electron transfers. Understanding hydrogen's ability to act in dual capacities helps us appreciate its ubiquity and utility in various chemical processes, including energy production, material synthesis, and environmental remediation.