Chemistry Q60 – JEE-MAIN 2025

Home Chemistry Periodicity & ElementsQuestion #538

The group 14 elements A and B have the first ionisation enthalpy values of 708 and 715 kJ mol

^{- 1}

respectively. The above values are lowest among their group members. The nature of their ions A

^{2 +}

and B

^{4 +}

respectively is

Clue 1 of 3: Ionization Enthalpy Trend

Recall the trend of first ionization enthalpy down Group 14 and the effect of d and f electrons on this trend.

🧠 Full Solution Path

Step 1: Identify Elements A and B✦ Active

The first ionization enthalpies for Group 14 elements are: Carbon (1086 kJ mol $^{- 1}$ ), Silicon (786 kJ mol $^{- 1}$ ), Germanium (761 kJ mol $^{- 1}$ ), Tin (708 kJ mol $^{- 1}$ ), and Lead (715 kJ mol $^{- 1}$ ). The question states that elements A and B have the lowest ionization enthalpy values among their group members. Comparing the given values with the actual values, A (708 kJ mol $^{- 1}$ ) corresponds to Tin (Sn), and B (715 kJ mol $^{- 1}$ ) corresponds to Lead (Pb).

Step 2: Analyze Stability of Oxidation States for Sn and Pb○ Expand

For Group 14 elements, the stability of the +2 oxidation state increases down the group, while the stability of the +4 oxidation state decreases. This is due to the inert pair effect, which becomes more prominent for heavier elements like Sn and Pb.

For Tin (Sn): Both +2 and +4 oxidation states are common. Sn $^{2 +}$ can be oxidized to Sn $^{4 +}$ (losing electrons), indicating that Sn $^{2 +}$ acts as a reducing agent.

For Lead (Pb): The +2 oxidation state is significantly more stable than the +4 oxidation state. Pb $^{4 +}$ is highly unstable and readily gets reduced to Pb $^{2 +}$ (gaining electrons), indicating that Pb $^{4 +}$ acts as a strong oxidizing agent.

💡 Teacher's Secret Hint

Remember that a species that loses electrons is a reducing agent, and a species that gains electrons is an oxidizing agent.

Step 3: Determine the Nature of A

^{2 +}

and B

^{4 +}

○ Expand

Based on the analysis:

A $^{2 +}$ is Sn $^{2 +}$ . Since Sn $^{2 +}$ can be oxidized to Sn $^{4 +}$ , it is a **reducing agent**.

B $^{4 +}$ is Pb $^{4 +}$ . Since Pb $^{4 +}$ readily gets reduced to Pb $^{2 +}$ , it is an **oxidizing agent**.

Therefore, the nature of their ions A $^{2 +}$ and B $^{4 +}$ respectively is reducing and oxidising.

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Chemistry Question 60 – JEE-MAIN 2025

Clue 1 of 3: Ionization Enthalpy Trend

🧠 Full Solution Path