Redox Reactions

The standard reduction potential affects the reducing agent's potency. The powerful nature of the reducing agent is shown by the large negative value.

Here, the fourth chemical reaction has the most lower E⁰ value so, it’ll be the strongest reducing agent.

A substance is a reducing agent when it loses electrons during a redox reaction and is oxidized to a higher valency state. A reducing agent is one of the reactants in an oxidation-reduction process; it decreases the other reactant by releasing electrons. If the reducing agent does not transfer electrons to other reactants in the reaction, the reduction process cannot occur.

Oxygen atoms are lost during reduction whereas electrons and hydrogen are obtained. Gaining oxygen while losing electrons and hydrogen is the process of oxidation. As a result, an element's oxidation state increases during oxidation, whereas it decreases during reduction.

A few characteristics of such reducing agents are–

• Electrons are often lost by reducing agents. Metals in the s-block of the periodic table are well-recognized for being effective reducers.
• The reducing agent oxidized after losing electrons, which led to the opposing reactant being reduced by receiving electrons.
• All effective reducing agents include species with low ionization energies as well as atoms with low electronegativity and a strong capacity of an atom or molecule to attract bonding electrons.
• All oxidation and reduction processes include the transfer of electrons.
• A material is considered to be reduced when it receives electrons and to be oxidized when it loses electrons.
• If a chemical has a significant propensity to lose electrons, it is referred to be a strong reducing agent.

To arrange the redox couples in the increasing order of their reducing strength, we need to look at the values of their standard electrode potentials ( ). The standard electrode potential indicates the ability of a species to gain electrons (reduction potential). A more negative value means a weaker tendency to reduce, and hence a stronger tendency to act as a reducing agent.
- For [A] Cu /Cu , V, so this species is a weak reducing agent.
- For [B] Ag /Ag, V, indicating an even weaker reducing agent than [A].
- For [D] Cr /Cr , V, indicating a stronger reducing agent than both [A] and [B].
- For [C] Ca /Ca, V, making this the strongest reducing agent.
Thus, the order of reducing strength from weakest to strongest is: B

In a redox reaction, the number of electrons involved in the reaction can be determined by looking at the changes in oxidation states of the reacting species.
In the reaction between and the sulphite ion , chromium (Cr) undergoes a change in oxidation state, and the number of electrons is involved in its reduction.
The balanced half-reaction for chromium in acidic medium is: The reduction half-reaction shows that for each mole of , 6 moles of electrons are involved. Since the problem asks for the number of electrons involved in producing 3.0 moles of the oxidised product, we multiply the number of electrons involved per mole of by 3: Thus, the number of moles of electrons involved is .