JEE Main 2026 · 2 Apr · Shift 2 · Chemistry Q70

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ChemistrySingle correct+4 / -1Question 70 of 75

Among $\ce{Fe^{2+}}$ , $\ce{Fe^{3+}}$ , $\ce{Cr^{2+}}$ and $\ce{Zn^{2+}}$ , the ion that shows positive borax bead test and with highest ionisation enthalpy is :

\ce{Fe^{2+}}

\ce{Zn^{2+}}

\ce{Cr^{2+}}

\ce{Fe^{3+}}

Answer and worked solution

Official answer: D

Borax bead test needs a coloured transition-metal ion: Fe²⁺, Fe³⁺ and Cr²⁺ qualify; Zn²⁺ (d¹⁰) does not.

Highest next ionisation enthalpy. $\ce{Fe^{3+}}$ is d⁵ (half-filled) with a higher charge, so removing another electron is hardest.

(D)

Topics:Flame and borax bead tests Transition element properties

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JEE Main 2026 · 2 Apr · Shift 2, Chemistry question 70