Question

You are told that metal \(A\) is a better reducing agent than metal B. What, if anything, can be said about \(A^{+}\) and \(B^{+} ?\) Explain.

Short answer

In short, if metal A is a better reducing agent than metal B, then its cation A⁺ has a higher reduction potential compared to B⁺, making A⁺ less stable than B⁺. This is because the stronger the reducing agent, the more easily it donates electrons and forms less stable cations, which have a higher tendency to accept electrons and get reduced.

Step-by-step solution

Understand the concept of reducing agents.

A reducing agent is a substance that reduces another compound by giving up electrons in a redox reaction. In this process, the reducing agent gets oxidized, which means it loses electrons. The strength of a reducing agent is determined by how readily it donates its electrons to other compounds. A stronger reducing agent donates electrons more easily, and thus has a higher tendency to get oxidized.

Relate the reducing ability to ion stability

When a metal loses its electrons and gets oxidized, it forms positive ions or cations. The more stable the cation formed, the less likely it is to accept electrons and return to its metallic form, which means that its reduction potential will be lower. On the other hand, a less stable cation will have a higher tendency to accept electrons and get reduced, corresponding to a higher reduction potential.

Compare the reduction ability of A⁺ and B⁺ based on the reducing ability of metals A and B

Since metal A is a better reducing agent than metal B, it means that metal A donates electrons more easily and has a higher tendency to get oxidized. From step 2, it can be inferred that cation A⁺ is less stable than cation B⁺, as A⁺ has a higher tendency to accept electrons and get reduced. Consequently, A⁺ has a higher reduction potential than B⁺. In conclusion, the relationship between the reducing ability of metals and their ions can be described: If metal A is a better reducing agent than metal B, then A⁺ has a higher reduction potential compared to B⁺ and is thus less stable than B⁺.

Key concepts

Redox Reactions

Redox reactions are fundamental processes in chemistry that involve the transfer of electrons between two species. The term 'redox' is a portmanteau of reduction and oxidation. These reactions are vital in a wide range of chemical, biological, and industrial processes.

In a redox reaction, one reactant is oxidized (loses electrons) and the other is reduced (gains electrons). The substance that donates electrons functions as a reducing agent, such as metal A in the given exercise. As it gives up electrons, it fosters the reduction of another substance, while itself experiencing oxidation. This electron transfer is crucial for the generation of energy in biological systems, as well as for many types of chemical manufacturing and materials processing.

A clear understanding of redox reactions helps in predicting reaction outcomes, such as identifying what happens to certain metals when they act as reducing agents. When metal A relinquishes electrons more readily than metal B, we can deduce important information about their respective ions' behaviors in solutions or reactions.

Oxidation and Reduction

Oxidation and reduction are two halves of a redox reaction. Oxidation refers to the loss of electrons by a substance, while reduction pertains to the gain of electrons. It's easy to remember this by the acronym 'OIL RIG': Oxidation Is Loss, Reduction Is Gain.

During a redox reaction, the oxidizing agent gains electrons and is reduced, while the reducing agent loses electrons and is oxidized. The oxidation state of an atom, ion, or molecule indicates the degree of oxidation or reduction it has undergone. When metals act as reducing agents, they undergo oxidation, increasing their oxidation state as they lose electrons and form cations.

Using metal A as an example, when it acts as a better reducing agent than metal B, it implies that metal A is more willing to be oxidized, thus it transfers electrons to other species more easily. This tells us about the relative ease with which each metal undergoes oxidation, a key concept in the context of redox reactions.

Reduction Potential

Reduction potential, also known as redox potential or electrode potential, measures the tendency of a chemical species to acquire electrons and be reduced. This is typically expressed in volts and is a quantitative indication of the substance's ability to gain electrons.

The reduction potential is influenced by several factors, such as the temperature, pressure, and concentrations of the species involved in the reaction. A higher reduction potential indicates a greater likelihood for a species to gain electrons. When comparing two cations, like A⁺ and B⁺, the cation with the higher reduction potential will be more inclined to gain electrons and be reduced back to its metallic form. This concept is vital when we interpret the exercise, showing that since A is a better reducing agent, A⁺, the cation of metal A, has a higher reduction potential as it is more inclined to accept electrons than B⁺.

Stability of Cations

The stability of cations is an essential concept when discussing reducing agents in chemistry. A cation is a positively charged ion, and its stability is often determined by factors such as the energy of ionization, size, and charge density.

A more stable cation is less likely to undergo further chemical reactions, such as accepting electrons to reduce back to its elemental form. Conversely, a less stable cation has a greater tendency to react and is often more reactive in seeking to acquire electrons to attain stability. When metal A is termed a better reducing agent than metal B, we infer that A⁺ is less stable due to its higher proclivity to accept electrons. This is rooted in its less favorable energetics for maintaining a cationic state, which makes it seek stability through reduction. Therefore, cation stability is inversely related to the reducing power of the corresponding metal.