JEE Main 2024 · 9 April · evening · Single correct · +4 / −1
Give below are two statements :
Statement I : The higher oxidation states are more stable down the group among transition elements unlike p-block elements.
Statement II : Copper can not liberate hydrogen from weak acids.
In the light of the above statements, choose the correct answer from the options given below :
- (a) Statement I is true but Statement II is false
- (b) Both Statement I and Statement II are false
- (c) Both Statement I and Statement II are true
- (d) Statement I is false but Statement II is true
Answer and solution
Answer (c) Both Statement I and Statement II are true
Solution
Chemistry ma’am · 4 steps
Down a d-block group high oxidation states get more stable, and copper sits above hydrogen in the series.
- Trend in d-block. Going down a transition metal group, the higher oxidation states become more stable. Cr^(VI) in Cr₂O₇²⁻ is a strong oxidising agent because it readily drops to Cr³⁺, while MoO₃ and WO₃ with +6 are stable and not oxidising.
- Trend in p-block. In the p-block it is the reverse. The inert pair effect makes the lower state more stable down the group: Pb²⁺ is more stable than Pb⁴⁺, and Tl⁺ is more stable than Tl³⁺. So Statement I is true.
- Copper and acids. To push out H₂, a metal must reduce H⁺, which needs a negative reduction potential. Copper has E°(Cu²⁺/Cu) = +0.34 V, so it cannot reduce H⁺ from any non-oxidising acid, let alone a weak one. Statement II is true.
- So. Both statements are true, which is option (c).
The idea to keep. Remember the mirror image: d-block favours higher oxidation states down a group, p-block favours lower ones (inert pair effect). A metal with positive E° cannot release H₂ from acids.
Answer from the NTA final answer key. Solution by PrepWiser.