Question

In which of the following reaction boron does not act as reducing agent? (a) \(\mathrm{B}+\mathrm{CO}_{2} \rightarrow\) (b) \(\mathrm{B}+\mathrm{Mg} \rightarrow\) (c) \(\mathrm{B}+\mathrm{HNO}_{3} \rightarrow\) (d) \(\mathrm{B}+\mathrm{SiO}_{2} \rightarrow\)

Short answer

Boron does not act as a reducing agent in reaction (b) \( \mathrm{B} + \mathrm{Mg} \rightarrow \).

Step-by-step solution

Understand Reduction and Oxidation

In a redox reaction, a reducing agent is a substance that donates electrons and becomes oxidized; it causes the reduction of another substance. Our task is to identify in which reaction boron does not donate electrons.

Analyze Reaction (a)

The reaction is \( \mathrm{B} + \mathrm{CO}_{2} \rightarrow \). Here, boron can act as a reducing agent, donating electrons to reduce \( \mathrm{CO}_{2} \) to \( \mathrm{CO} \).

Analyze Reaction (b)

The reaction is \( \mathrm{B} + \mathrm{Mg} \rightarrow \). Boron does not act as a reducing agent here because \( \mathrm{Mg} \) is a stronger reducing agent, so boron does not donate electrons to \( \mathrm{Mg} \). Thus, boron cannot reduce \( \mathrm{Mg} \) and doesn't act as a reducing agent in this reaction.

Analyze Reaction (c)

The reaction is \( \mathrm{B} + \mathrm{HNO}_{3} \rightarrow \). In this reaction, boron can donate electrons to \( \mathrm{HNO}_{3} \), which means boron is acting as a reducing agent.

Analyze Reaction (d)

The reaction is \( \mathrm{B} + \mathrm{SiO}_{2} \rightarrow \). Boron can reduce \( \mathrm{SiO}_{2} \) by donating electrons to form \( \mathrm{Si} \), acting as a reducing agent.

Key concepts

Reducing Agent

In the world of redox reactions, a reducing agent plays a vital role by donating electrons to another substance. When it gives away electrons, it undergoes oxidation itself. This may sound quite complex, but think of it simply as a giver that makes another element improve by losing some of its own substance. These marvels of chemistry essentially facilitate the process of reduction for the other element.

• Electron Donation: The key task of a reducing agent is to donate electrons.
• Oxidation Process: By donating electrons, the reducing agent itself gets oxidized.
• Reduction Effect: The receiving substance undergoes reduction, gaining those electrons.

In the context of our exercise, we analyze how boron behaves in different reactions. In some reactions, boron gladly donates electrons, thereby acting as a reducing agent. While in the presence of a mightier reducing element, like magnesium, boron takes a step back.

Boron Chemistry

Boron, an intriguing element, often finds its place as a reducing agent due to its ability to donate electrons. This semi-metal is noteworthy for its odd position on the periodic table, not quite fitting in with typical metals or non-metals, giving it unique reactive properties.

• Chemical Versatility: Boron's position in the periodic table allows it to sometimes behave as a non-metal and sometimes show metal-like properties.
• Electron Donation: It can act as a reducing agent by donating electrons in reactions.
• Practical Examples: In reactions like \(\mathrm{B}+\mathrm{CO}_{2} \rightarrow\) and \(\mathrm{B}+\mathrm{HNO}_{3} \rightarrow\), boron performs its reducing role.

These unique properties also allow it to be quite selective about which reactions to involve itself in as a reducing agent. As explored in the exercise, boron showed its selective nature by stepping back in the presence of magnesium.

Oxidation States

Understanding oxidation states can initially seem daunting, but they are simply a way to keep track of how many electrons an atom gains or loses during a reaction. To break it down, the oxidation state is the hypothetical charge an atom would have if all bonds were 100% ionic.

• Tracking Electrons: Oxidation states help in determining how many electrons are gained or lost by atoms.
• Indicator of Redox Reaction: A change in oxidation states indicates a redox reaction.
• Boron’s Oxidation Behavior: Generally, boron shifts oxidation states as it participates in redox reactions, often acting as a reducing agent.

In the exercise, understanding the oxidation states can help identify when boron is acting differently in various reactions. In cases like boron interacting with magnesium, as opposed to other agents, measuring these states highlights why boron may not donate electrons, distinguishing the reaction types effectively.