15. The magnetic moment of a green salt Kₙ[VF₆] is 2.79 μB (Bohr magneton number). What should be n? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

1. The Nobel Prize in Chemistry in 2022 was awarded to click chemistry, or the azide-alkyne cycloaddition to connect two molecular fragments. For their initial discovery, what metal ion was required as a catalyst for this reaction to proceed at a milder condition? (A) Cu(I) (B) Zn(II) (C) Fe(II) (D) Fe(III) (E) Mo(II)