Question

(a) Use the following reactions to arrange the elements \(\mathbf{A}, \mathbf{B}, \mathbf{C}\). and \(\mathrm{D}\) in order of their decreasing ability as reducing agents: \(\mathrm{C}+\mathrm{B}^{+}\) \(\mathrm{C}^{+}+\mathrm{B}\) \(\mathrm{A}^{+}+\mathrm{D} \longrightarrow\) No reaction \(\mathrm{C}^{+}+\mathrm{A} \longrightarrow\) No reaction \(\mathrm{D}+\mathrm{B}^{+} \longrightarrow \mathrm{D}^{+}+\mathrm{B}\) (b) Which of the following reactions would you expect to occur according to the activity series you established in part (a)? (1) \(\mathrm{A}^{+}+\mathrm{C} \longrightarrow \mathrm{A}+\mathrm{C}^{+}\) (2) \(\mathrm{A}^{+}+\mathrm{B} \longrightarrow \mathrm{A}+\mathrm{B}^{-}\)

Short answer

(a) D > B ≥ C > A; (b) Only reaction (2) occurs.

Step-by-step solution

Analyze Reaction 1

In the given reaction, C + B⁺, no specific direction is given, which indicates a possible equilibrium (C + B⁺ ↔ C⁺ + B). Both the forward and backward reactions might be possible, suggesting that C and B have comparable ability to oxidize or reduce each other.

Analyze Reaction 2

For the reaction C⁺ + B and C + B⁺, we see that the reaction is similar to the one described in Step 1. Therefore, C and B can oxidize and reduce each other, showing comparable reducing strengths.

Analyze Reaction 3

In the next reaction, A⁺ + D → No reaction, A is unable to reduce D⁺. This means D is a stronger reducing agent than A, as D is not being oxidized by A.

Analyze Reaction 4

For the reaction C⁺ + A → No reaction, C is unable to oxidize A, suggesting that A has stronger reducing ability than C. A is a stronger reducing agent than C.

Analyze Reaction 5

In the reaction D + B⁺ → D⁺ + B, D is able to reduce B⁺ to B, indicating that D is a stronger reducing agent than B. D has greater reducing power compared to B.

Establish Activity Series

Based on the analysis from previous steps, we have: - D is a stronger reducing agent than B (from Reaction 5). - D is a stronger reducing agent than A (from Reaction 3 combined indirectly through lack of reactivity between A and C). - A is a stronger reducing agent than C (from Reaction 4). Thus, the order of elements in decreasing ability as reducing agents is: **D > B ≥ C > A**

Evaluate Reaction 1 from Part (b)

Considering the established activity series D > B > C > A, we find that C is a weaker reducing agent than A. Therefore, the reaction A⁺ + C → A + C⁺ is not expected to occur, as C cannot reduce A⁺.

Evaluate Reaction 2 from Part (b)

In line with the activity series, B is a stronger reducing agent than A. Therefore, A⁺ + B → A + B⁺ is feasible, and this reaction is expected to occur.

Key concepts

Reducing Agents

In chemistry, a reducing agent is a substance that donates electrons in a chemical reaction, leading to the reduction of another substance. This means that a reducing agent is oxidized, increasing its oxidation state by losing electrons.
Reducing agents are crucial in redox reactions, where they help to draw out electrons from the oxidized material. The strength of a reducing agent is based on its ability to lose electrons and is often influenced by its position in the activity series.
The activity series is a handy tool that ranks elements by their reducing ability, allowing us to predict the outcome of displacement reactions. For example, in our exercise, the series derived as **D > B ≥ C > A** shows that "D" is the strongest reducing agent. When analyzing chemical reactions, elements higher in the activity series can reduce those below them, but not vice versa.

Chemical Reactions

Chemical reactions are processes where substances, called reactants, transform into different substances known as products. This transformation involves breaking of old bonds and forming of new ones.
For instance, in the reactions given in the original exercise, we analyzed changes such as:

• C + B⁺ ↔ C⁺ + B, indicating equilibrium with no decisive direction
• D + B⁺ → D⁺ + B, showcasing a straightforward electron transfer

Such reactions can be categorized based on the nature of the changes, such as synthesis, decomposition, single displacement, or double displacement.
In redox reactions, like those in our example, a specialized type of chemical reaction occurs where oxidation and reduction happen simultaneously. These reactions heavily rely on the position of elements in the activity series to predict possible changes.

Oxidation-Reduction Reactions

Oxidation-reduction reactions, often called redox reactions, are a type of chemical reaction involving the transfer of electrons between two substances. In these reactions, one substance loses electrons (oxidation), and another gains electrons (reduction).
An easy way to remember is using the mnemonic OIL RIG: Oxidation Is Loss, Reduction Is Gain.

• Oxidation involves an increase in oxidation state (loss of electrons).
• Reduction is a decrease in oxidation state (gain of electrons).

In our exercise, by analyzing reactions like A⁺ + D → No reaction, we can determine which elements can act as effective reducing agents. "D" could not be oxidized by "A," indicating "D" is a better reducing agent.
By using the activity series, we can establish which reactions are feasible. This helps predict whether a reaction like A⁺ + C is possible. "A" cannot gain electrons from "C," hence this reaction does not proceed.
Redox reactions are important in various applications such as energy production, metal extraction, and biological processes, demonstrating their vast significance in both theoretical and practical chemistry.