Problem 16 - Chemistry: The Central Science in SI Units, Global Edition

Question

Indicate whether each of the following statements is true or false: (a) If something is reduced, it is formally losing electrons. (b) A reducing agent gets oxidized as it reacts. (c) An oxidizing agent is needed to convert \(\mathrm{CO}\) into \(\mathrm{CO}_{2}\).

Step-by-Step Solution

Answer

Statement (a) is False. If something is reduced, it is formally gaining electrons, not losing them. Statement (b) is True. A reducing agent gets oxidized as it reacts, meaning that it loses electrons itself while helping other substances gain electrons. Statement (c) is True. An oxidizing agent is needed to convert \(\mathrm{CO}\) into \(\mathrm{CO}_{2}\), as the carbon atom in \(\mathrm{CO}\) needs to undergo oxidation (lose electrons) to bond with the additional oxygen atom, forming \(\mathrm{CO}_{2}\).

Step 1: Statement (a) Analysis

It's important to remember the mnemonic "LEO goes GER" - Loss of Electrons is Oxidation, and Gain of Electrons is Reduction. Let's use this knowledge to determine if statement (a) is true or false.

Step 2: Statement (a) Conclusion

Statement (a) is False. If something is reduced, it is formally gaining electrons, not losing them.

Step 3: Statement (b) Analysis

To analyze statement (b), we need to understand the role of a reducing agent. A reducing agent reduces other substances while it undergoes oxidation. Let's determine if the statement is true or false.

Step 4: Statement (b) Conclusion

Statement (b) is True. A reducing agent gets oxidized as it reacts, meaning that it loses electrons itself while helping other substances gain electrons.

Step 5: Statement (c) Analysis

For statement (c), we are looking at the conversion of \(\mathrm{CO}\) into \(\mathrm{CO}_{2}\) and whether an oxidizing agent is necessary. An oxidizing agent takes electrons from other substances, making the other substances lose electrons (undergo oxidation). In this case, we want to find out if going from \(\mathrm{CO}\) to \(\mathrm{CO}_{2}\) requires an oxidizing agent.

Step 6: Statement (c) Conclusion

Statement (c) is True. An oxidizing agent is needed to convert \(\mathrm{CO}\) into \(\mathrm{CO}_{2}\), as the carbon atom in \(\mathrm{CO}\) needs to undergo oxidation (lose electrons) to bond with the additional oxygen atom, forming \(\mathrm{CO}_{2}\).

Key Concepts

Reduction

Reduction is a key concept in chemistry, particularly in redox reactions. It involves the gain of electrons by a molecule, atom, or ion. When a substance undergoes reduction, it acquires electrons, which decreases its oxidation state.
This process often pairs with oxidation, as one substance gains the electrons that another loses. For example:
- When copper ions ( ext{Cu}^{2+}) in a solution gain electrons, they transform into copper metal (Cu). Here, copper is reduced because it gains electrons.
Reduction doesn't occur in isolation; it always accompanies an oxidation process. This unity between reduction and oxidation forms what is known as a redox reaction. An easy way to remember reduction is to think of it as gaining "negativity" in the form of electrons.

Oxidation

Oxidation is the process where a substance loses electrons, leading to an increase in its oxidation state. This is the other half of a redox reaction.
It is crucial to remember that oxidation doesn't just mean combining with oxygen. It refers to the loss of electrons, no matter the type of atom. Let's consider an example:
- When iron (Fe) reacts with oxygen in the air, it forms rust ( ext{Fe}_2 ext{O}_3). Iron loses electrons to oxygen in this process, undergoing oxidation.
Oxidation is often remembered using the "LEO" part of the "LEO goes GER" mnemonic, indicating "Loss of Electrons is Oxidation." Oxidation reactions are significant not only in chemistry labs but also in biological processes, metallurgy, and everyday phenomena like wood burning.

Reducing Agent

A reducing agent, also known as a reductant, is a substance that donates electrons to another in a redox reaction. By doing so, it helps another substance to undergo reduction, while it itself gets oxidized.
It plays a crucial role in facilitating redox reactions, acting as an electron provider. Understanding the actions of a reducing agent involves identifying it as the donor of electrons:
- In the reaction between hydrogen (H_2) and fluorine (F_2) to form hydrogen fluoride (HF), hydrogen acts as a reducing agent. It donates electrons to fluorine, allowing fluorine to be reduced, while hydrogen itself becomes oxidized.
Reducing agents are sometimes metals or other elements that can easily lose electrons. Their identification is essential when analyzing reactions using the concept of electron transfer.

Oxidizing Agent

An oxidizing agent, or oxidant, causes another substance to lose electrons, effectively extracting electrons from it. In doing so, the oxidizing agent is reduced itself.
These agents play a vital role in initiating and maintaining redox reactions. For instance:
- Consider the reaction where ext{KMnO}_4 oxidizes ext{Fe}^{2+} to ext{Fe}^{3+}. Here, ext{KMnO}_4 behaves as the oxidizing agent, accepting electrons from ext{Fe}^{2+}, which leads to the oxidation of iron. It's handy to think of oxidizing agents as electron grabbers. This attribute allows them to appear in numerous chemical reactions, from simple chemical processes to complex biological systems. Understanding them helps clarify how substances transform during redox reactions.