Problem 35 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Statement-1 : \(\mathrm{Pb}^{+4}\) compounds are stronger oxidising agents than \(\mathrm{Sn}^{4+}\) compounds [2008] Statement-2 : The higher oxidation states for the group 14 elements are more stable for the heavier members of the group due to 'inert pair effect'.

Step-by-Step Solution

Answer

Statement-1 is true; Statement-2 is false.

Step 1: Understand Oxidation States

Lead ( pb ext{Pb} ) and tin ( ext{Sn} ) are elements in group 14 of the periodic table. The elements in group 14 can exist in oxidation states from +2 to +4. Both Pb and Sn can form +4 oxidation state compounds.

Step 2: Compare Stability due to the Inert Pair Effect

The 'inert pair effect' refers to the tendency of the s-electron pair to remain in a non-ionized state. This effect becomes more pronounced in heavier elements of group 14, like lead. As a result, the +2 oxidation state becomes more stable in heavier elements, reducing the stability of the +4 oxidation state.

Step 3: Evaluate Oxidising Strength

Since pb^{+4} prefers to revert to the more stable +2 state, it acts as a stronger oxidizing agent, as it tends to gain two electrons to achieve its stable configuration. In contrast, ext{Sn}^{4+} is stable and does not readily accept electrons, making it a weaker oxidizing agent.

Step 4: Analyze the Statements

Using the understanding of the inert pair effect and its impact on the stability and oxidizing strength of high oxidation states: Statement-1 is true because pb^{+4} compounds are stronger oxidizing agents, and Statement-2 is false, as the inert pair effect actually enhances the +2 stability rather than the higher states.

Key Concepts

Oxidation States

Oxidation states represent the degree of oxidation an atom undergoes within a compound. For elements in Group 14, they can exhibit oxidation states ranging from +2 to +4. Understanding this concept is pivotal to comprehending the chemical behavior of these elements.
While carbon typically shows a +4 state, heavier counterparts like lead (Pb) and tin (Sn) also form compounds in both +2 and +4 states. The oxidation state is determined by the loss or sharing of valence electrons during chemical reactions.

• In the +2 state, elements have lost fewer electrons compared to the +4 state.
• The stability of these states can significantly differ based on electronic configurations and other atomic properties such as the 'inert pair effect'.

Pb and Sn frequently form +4 oxidation state compounds, yet the stability of these compounds can shift due to underlying atomic factors, influencing their role in reactions.

Group 14 Elements

Group 14 of the periodic table consists of carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). These elements are known as tetrels and feature prominently in understanding chemical bonding and oxidation states.
As you move down the group, the atomic size increases and metallic character becomes more pronounced. While carbon is non-metallic, lead and tin exhibit metallic behavior, reflecting in their compound formation and preferred oxidation states.
One key factor for these elements, especially for the heavier ones, is the 'inert pair effect', which stabilizes the +2 oxidation state over the +4 state. This effect is less observed in lighter elements like carbon and silicon.

• Carbon tends to form stable +4 oxidation state compounds.
• Lead, more often than not, forms more stable compounds in the +2 state due to the inert pair effect.
• Heavier elements have more complex electron cloud interactions leading to unique bonding behavior.

Oxidizing Agents

Oxidizing agents are substances that readily accept electrons, facilitating the oxidation of other molecules within a chemical reaction. The nature of an oxidizing agent is determined by its oxidation state and the stability of its reduced form.
For lead ( ext{Pb}) and tin ( ext{Sn}) in high oxidation states like +4, the potential to act as oxidizing agents varies greatly. Due to the inert pair effect, ext{Pb}^{+4} compounds are more inclined to accept electrons and revert to their stable +2 state, thereby making them strong oxidizing agents.

• Pb^{+4} compounds act powerfully as they seek to attain electron stability by gaining electrons.
• Sn^{4+} often remains more stable in its current state, making it a weaker oxidizing agent.
• The difference in oxidizing ability arises from the specific electrochemical stability balance in these atoms.

Understanding these functions helps in predicting and utilizing these compounds in chemical reactions effectively.