CBSE 2026 · Region 3 · Set 2 · Q13 · 1 mark
Assertion (A) : Separation of Zr and Hf is difficult. Reason $\displaystyle (R)$ : Zr and Hf have almost identical atomic and ionic radii due to lanthanoid contraction.
Official answer
From CBSE’s own marking scheme for this paper.
(A)
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
The d-and f-Block ElementsThe LanthanoidsUnderstandassertion_reasonmedium
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CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.