Test: Redox reactions & Equivalent Weight (11 August) - JEE MCQ

A disproportionation reaction is a particular type of redox reaction in which a single compound is transformed into two different compounds, one being reduced and the other being oxidized.

The decomposition of hydrogen peroxide to form water and oxygen is a classic example of a disproportionation reaction.

The oxidation number is a concept in chemistry that helps us to keep track of electrons in an atom. It is based on the assumption that the electrons in a covalent bond belong entirely to the more electronegative element. This is a simplifying assumption that allows us to track electron movement and make predictions about chemical reactions.

P4 is undergoing oxidation as well as reduction. As oxidation number of P₄ is 0 in reactant and it increases to +3 in H₂PO₂^- and decreases to -3 in PH₃

Explanation of Highest Value of Oxidation Number Changes from 1 to 7

The highest value of oxidation number changes from 1 to 7 across the third period in the periodic table. This is due to the following reasons:

• The Atoms of Transition Elements:Transition metals are those elements located in the d-block of the periodic table. They have varying oxidation states, but they do not usually reach an oxidation state of 7. Their oxidation states primarily range between +2 and +3, although some can reach states of +4 or +5.
• The First Three Groups:The first three groups of the periodic table include alkali metals, alkaline earth metals, and boron group elements. These groups generally have oxidation states of +1, +2, and +3 respectively. They do not reach an oxidation state of 7.
• In Alkaline Earth Metals:Alkaline earth metals are the elements in the second group of the periodic table. These elements generally have an oxidation state of +2 due to the presence of two valence electrons which are readily lost in chemical reactions.
• Across the Third Period in the Periodic Table:The elements in the third period of the periodic table show a wider range of oxidation states, which can vary from +1 to +7. This is due to the presence of both s and p orbitals in their valence shell, which allows the elements to lose or gain more electrons in chemical reactions. Therefore, across the third period in the periodic table, the highest value of oxidation number changes from 1 to 7.

The standard electrode potential, E₀, is a measure of the tendency of a chemical species to be reduced. The higher the E₀ value, the greater the tendency for reduction.

In a redox reaction, the chemical species that gets reduced acts as the oxidising agent. Therefore, the species with the highest E₀ value will be the strongest oxidising agent.

Given the E0 values:

• Fe³⁺ / Fe²⁺ = +0.77V
• I₂(s) / I^- = +0.54V
• Cu²⁺ / Cu = +0.34V
• Ag⁺ / Ag = +0.80V

From the given values, it is clear that Ag+ / Ag has the highest E₀ value (+0.80V). Therefore, Ag+ is the strongest oxidising agent among the given options.

Conclusion:

• Ag+ is the strongest oxidising agent because it has the highest standard electrode potential (E₀) value among the given species.
• Remember, the higher the E₀ value, the greater the tendency of the species to be reduced, and hence, stronger is its oxidising power.

Change in oxidation number = 24 units