Question

What will be the order of decreasing reducing nature for the given metals? (a) \(\mathrm{Zn}>\mathrm{Na}>\mathrm{Fe}>\mathrm{Mg}>\mathrm{Cu}>\mathrm{Ag}\) (b) \(\mathrm{Cu}>\mathrm{Fe}>\mathrm{Mg}>\mathrm{Zn}>\mathrm{Na}>\mathrm{Ag}\) (c) \(\quad \mathrm{Ag}>\mathrm{Cu}>\mathrm{Fe}>\mathrm{Zn}>\mathrm{Mg}>\mathrm{Na}\) (d) \(\mathrm{Na}>\mathrm{Mg}>\mathrm{Zn}>\mathrm{Fe}>\mathrm{Cu}>\mathrm{Ag}\)

Short answer

The correct order of decreasing reducing nature is (d) \(\mathrm{Na}>\mathrm{Mg}>\mathrm{Zn}>\mathrm{Fe}>\mathrm{Cu}>\mathrm{Ag}\).

Step-by-step solution

Understand Reducing Nature

The reducing nature of a metal refers to its ability to donate electrons and reduce other substances. A more reactive metal, which more readily loses electrons, is a stronger reducing agent.

Assessing Standard Reduction Potentials

The standard reduction potential of metals is inversely related to their reducing power. The lower the reduction potential, the stronger the reducing agent. This means metals with lower reduction potentials are more powerful reducers.

Ordering Metals by Reducing Strength

We know that among the given metals, the activity series (from strongest to weakest reducing agents) is as follows: \(\mathrm{Na} > \mathrm{Mg} > \mathrm{Zn} > \mathrm{Fe} > \mathrm{Cu} > \mathrm{Ag}\). The metal that most readily loses an electron is the strongest reducing agent. Therefore, sodium (Na) is the strongest and silver (Ag) is the weakest reducing agent listed.

Key concepts

Understanding Standard Reduction Potentials

The concept of standard reduction potentials is pivotal in understanding the reducing nature of metals. This chemical property measures the tendency of a chemical species to acquire electrons and thus be reduced. Each element has an associated standard reduction potential, often listed in a table known as the standard reduction potential table.

Here's the fundamental idea: the more negative the reduction potential, the more readily the element will lose electrons and behave as a reducing agent. For example, lithium, with a very negative standard reduction potential, is a better reducing agent than copper, with a less negative value.

When comparing metals, we can use this principle to predict their reducing nature. A metal with a lower (more negative) standard reduction potential will more willingly give up its electrons to another substance, thereby reducing that substance. In terms of the exercise at hand, understanding and analyzing the standard reduction potentials of the involved metals can guide us to the correct ordering, with the strongest reducing metals being first in the series.

Reactivity Series and Reducing Nature

The reactivity series, also known as the activity series, is a list of metals arranged in order of their 'reactivity' from highest to lowest. Reactivity in this context refers to the ease with which a metal can lose electrons, forming positive ions. This characteristic is directly related to the reducing power of the metal.

A metal high on the reactivity series is a strong reducing agent and can easily donate electrons to substances in chemical reactions. Conversely, metals lower on the series are weaker reducers. Thus, the reactivity series allows us to predict how metals will react, particularly in displacement reactions and redox reactions.

If we take sodium (Na), positioned high in the reactivity series, we can infer its high reducing power, as it loses electrons more easily than silver (Ag), which is lower in the series. Therefore, when prioritizing metals by their reducing nature, as needed in the exercise, we can rely on the positions in the reactivity series as a definitive guide.

Electrochemical Activity and Reducing Agents

Electrochemical activity in metals indicates their ability to participate in electron transfer during a chemical reaction. The reducing nature of a metal is tied to its electrochemical activity; metals that are good at giving up their electrons are deemed electrochemically active.

Metals that have a high electrochemical activity are strong reducing agents since they can readily donate electrons to another species. In the context of a redox reaction, the metal, acting as an anode, gets oxidized by losing electrons, while the cathode is reduced as it gains those electrons. Factors such as atomic structure, as well as the energy required to remove an electron from the atom, affect a metal’s electrochemical activity.

We can connect this to the exercise by recognizing that the metals listed vary in their ability to act as reducing agents based on their electrochemical activity. When sorted by decreasing reducing nature, metals with more electrochemical activity, such as sodium (Na), would naturally precede those like silver (Ag) that are less active.