Problem 2 - Chemical Principles in the Laboratory

Question

Substances \(A_{2}, B_{2}\), and \(C_{2}\) can all act as oxidizing agents. In solution, \(A_{2}\) is green, \(B_{2}\) is yellow, and \(C_{2}\) is red. In the reactions in which they participate, they are reduced to A^{ - } \(, B^{2}\), and \(C\) - ions, all of which are colorless. When a solution of \(C_{2}\) is mixed with one containing \(B^{-}\) ions, the color changes from red to yellow. Which species is oxidized?_________ . Which is reduced? _______ . When a solution of \(C_{2}\) is mixed with one containing \(A^{-}\) ions, the color remains red. Is \(C_{2}\) a better oxidizing agent than \(A_{2} ?\) _______ . Is \(C_{2}\) a better oxidizing agent than \(B_{2} ?\) ________ . Arrange \(A_{2}, B_{2},\) and \(C_{2}\) in order of increasing strength as an oxidizing agent. __________ < ___________ < _________ .

Step-by-Step Solution

Answer

Species oxidized: \(B^{-}\). Species reduced: \(C_{2}\). No, \(C_{2}\) is not better than \(A_{2}\). Yes, \(C_{2}\) is better than \(B_{2}\). Order: \(B_{2}\) < \(C_{2}\) < \(A_{2}\).

Step 1: Understanding the Problem

The problem involves substances \(A_{2}, B_{2},\) and \(C_{2}\) acting as oxidizing agents and being reduced in reactions. The essence is to determine which species is oxidized and which is reduced, and to compare the oxidizing strength based on observable color changes.

Step 2: Color Change Analysis for Reaction with B^-

When \(C_{2}\) (red) is mixed with \(B^{-}\), the solution turns yellow, indicating \(C_{2}\) is reduced to \(C^{-}\) (colorless) and \(B^{-}\) is oxidized to \(B_{2}\). Thus, \(C_{2}\) is the oxidizing agent, and \(B^{-}\) is the reducing agent.

Step 3: Color Change Analysis for Reaction with A^-

When \(C_{2}\) (red) is mixed with \(A^{-}\), the color remains red, indicating that \(C_{2}\) does not oxidize \(A^{-}\). This suggests \(C_{2}\) is not a stronger oxidizing agent than \(A_{2}\), as there is no observable reduction.

Step 4: Determine Relative Oxidizing Strength

Since \(C_{2}\) could oxidize \(B^{-}\) but not \(A^{-}\), we conclude \(A_{2}\) is a stronger oxidizing agent than \(C_{2}\), and \(C_{2}\) is a stronger oxidizing agent than \(B_{2}\). Therefore, the order of increasing oxidizing strength is: \(B_{2}\) < \(C_{2}\) < \(A_{2}\).

Key Concepts

Chemical Reactions

A chemical reaction is a process where substances, known as reactants, undergo a transformation to form different substances called products. During this process, the bonds between atoms in the reactants are broken and new bonds are formed in the products.

• The reaction in this specific exercise involves oxidation-reduction processes.
• These reactions can be identified by observing color changes, which might indicate changes in the oxidation state of substances.

For instance, when substances like \(C_{2}\) (red in color) and \(B^{-}\) (colorless) react, the color change to yellow shows a chemical reaction is occurring. This transformation signifies that electrons are being transferred between these substances, altering their chemical structure. Chemical reactions are influenced by various factors such as temperature, concentration, and presence of catalysts. In this scenario, the different colors of the substances can help identify the occurrence and type of chemical reaction taking place.

Oxidation and Reduction

Oxidation and reduction, often referred to as redox reactions, are key concepts in understanding the exchange of electrons between substances in a chemical reaction.

• Oxidation involves the loss of electrons from a substance.
• Reduction involves the gain of electrons by a substance.

In the exercise, the substance \(C_{2}\) undergoes reduction when it changes from red to colorless (\(C^{-}\)), indicating it gains electrons. Conversely, \(B^{-}\) is oxidized when it shifts from colorless to yellow (\(B_{2}\)), suggesting it loses electrons during the reaction.The terms can be easily remembered using the acronym "OIL RIG": Oxidation Is Loss, Reduction Is Gain. This means oxidation happens when a substance loses electrons and reduction occurs when a substance gains electrons. Understanding which substance is oxidized and which is reduced is crucial for determining the type of redox reaction and predicting the outcome of the reaction.

Redox Reactions

Redox reactions, short for reduction-oxidation reactions, describe a process where oxidation and reduction occur simultaneously. These reactions are fundamental in many chemical and biological processes.

• An oxidizing agent is a substance that gains electrons (is reduced) and thereby causes another substance to lose electrons (be oxidized).
• A reducing agent is a substance that loses electrons (is oxidized) and thereby causes another substance to gain electrons (be reduced).

In the given exercise, \(C_{2}\) acts as an oxidizing agent when it gains electrons from \(B^{-}\), which acts as a reducing agent. The color changes observed during the reactions provide visual evidence of the redox processes occurring. By comparing different substances like \(A_{2}, B_{2},\) and \(C_{2}\), one can determine their relative strength as oxidizing agents. This is based on their ability to cause other substances to oxidize. Ultimately, understanding redox reactions helps in predicting the behavior of substances in chemical reactions, which is essential for solving many real-world chemical and environmental challenges.