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Chemistry · Periodicity of Elements and Periodic Properties

JEE Main 2026 — 22 January, Morning Shift — Question 53

A 'p'-block element (E) and hydrogen form a binary cation (EHx)+(\mathrm{EH_x})^+, while EH3\mathrm{EH_3} on treatment with K2HgI4\mathrm{K_2HgI_4} in alkaline medium gives a precipitate of basic mercury(II)amido-iodine. Given below are first ionisation enthalpy values (kJ mol−1)(kJ\,mol^{-1}) for first element each from group 13, 14, 15 and 16. Identify the correct first ionisation enthalpy value for element E.

  1. Option A:

    1312

  2. Option B:

    1086

  3. Option C:

    1402

    Correct
  4. Option D:

    801

Answer: C

Step-by-step solution

K2HgI4\mathrm{K_2HgI_4} in alkaline medium is Nessler’s reagent.

It gives brown precipitate with NH3\mathrm{NH_3}. Thus EH3\mathrm{EH_3} must be NH3\mathrm{NH_3}.

Therefore element E\mathrm{E} is nitrogen (Group 15).

First ionisation enthalpy of nitrogen is approximately 1402 kJ mol−11402 \, \mathrm{kJ\,mol^{-1}}.

Hence, the correct value corresponds to nitrogen is 1402 kJ mol−11402 \, \mathrm{kJ\,mol^{-1}}.

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Paper
22 January, Morning Shift
Subject
Chemistry
Chapter
Periodicity of Elements and Periodic Properties
Topic
Periodicity in Chemical Properties (Ionization Energy, Electron Affinity, Electronegativity)

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