JEE Main · 2025 · 29 Jan 2025 · Shift 1 · Classification of Elements and Periodicity

An element 'E' has the ionisation enthalpy value of

374 kJ mol^{- 1}

. 'E' reacts with elements A, B, C and D with electron gain enthalpy values of

- 328, - 349

, -325 and

- 295 kJ mol^{- 1}

, respectively.
The correct order of the products EA, EB, EC and ED in terms of ionic character is:

(A) $EB > EA > EC > ED$ ✓ Correct
(B) $ED > EC > EA > EB$
(C) $EA > EB > EC > ED$
(D) $ED > EC > EB > EA$

Answer: (A)

Solution

Ionic character in the product forms most completely when the energy cost of ionising the cation is well offset by the energy released on forming the anion — the smaller the gap between the ionisation enthalpy of E (374 kJ/mol) and the magnitude of the partner's electron gain enthalpy, the more favourable the electron transfer, and the greater the ionic character of the resulting salt.

Differences: EA:

374 - 328 = 46

; EB:

374 - 349 = 25

; EC:

374 - 325 = 49

; ED:

374 - 295 = 79

.

Smaller difference means greater ionic character, giving the order EB > EA > EC > ED.

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JEE Main · 2025 · 29 Jan 2025 · Shift 1 · Classification of Elements and Periodicity

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