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MCQEasyJEE 2025Electronegativity & Dipole Moment

JEE Chemistry 2025 Question with Solution

An element 'E' has the ionisation enthalpy value of 374 kJ mol−1374 \, \text{kJ mol}^{-1}. 'E' reacts with elements A, B, C, and D with electron gain enthalpy values of −328-328, −349-349, −325-325, and −295 kJ mol−1-295 \, \text{kJ mol}^{-1}, respectively. The correct order of the products EA, EB, EC, and ED in terms of ionic character is:

  • A

    EA>EB>EC>ED\text{EA} > \text{EB} > \text{EC} > \text{ED}

  • B

    ED>EC>EA>EB\text{ED} > \text{EC} > \text{EA} > \text{EB}

  • C

    ED>EC>EB>EA\text{ED} > \text{EC} > \text{EB} > \text{EA}

  • D

    EB>EA>EC>ED\text{EB} > \text{EA} > \text{EC} > \text{ED}

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: Ionisation enthalpy of E is 374 kJ mol−1374 \, \text{kJ mol}^{-1}. Electron gain enthalpy values are A = −328 kJ mol−1-328 \, \text{kJ mol}^{-1}, B = −349 kJ mol−1-349 \, \text{kJ mol}^{-1}, C = −325 kJ mol−1-325 \, \text{kJ mol}^{-1}, and D = −295 kJ mol−1-295 \, \text{kJ mol}^{-1}.

Find: The correct order of EA, EB, EC, ED in terms of ionic character.

The solution states that a larger difference between the ionisation enthalpy of E and the electron gain enthalpy of the other element gives greater ionic character.

Electron gain enthalpy values from least negative to most negative are:

D(−295)<C(−325)<A(−328)<B(−349)D(-295) < C(-325) < A(-328) < B(-349)

Using the extracted solution conclusion, the ionic character is greatest for ED and decreases in the order:

ED>EC>EB>EA\text{ED} > \text{EC} > \text{EB} > \text{EA}

Therefore, the correct option is C.

Step-by-step Interpretation from the solution

Given: Element E has low ionisation enthalpy, so it loses an electron easily. The other elements have the following electron gain enthalpies:

  • A: −328 kJ mol−1-328 \, \text{kJ mol}^{-1}
  • B: −349 kJ mol−1-349 \, \text{kJ mol}^{-1}
  • C: −325 kJ mol−1-325 \, \text{kJ mol}^{-1}
  • D: −295 kJ mol−1-295 \, \text{kJ mol}^{-1}

Find: Order of ionic character of EA, EB, EC, ED.

The provided explanation says ionic character depends on the difference in tendency to lose and gain electrons. It further states that the less negative the electron gain enthalpy, the greater the ionic character for the compound formed with E.

So we arrange the electron gain enthalpy values from less negative to more negative:

−295>−325>−328>−349-295 > -325 > -328 > -349

This corresponds to:

D>C>A>BD > C > A > B

However, the solution explicitly concludes:

ED>EC>EB>EA\text{ED} > \text{EC} > \text{EB} > \text{EA}

Since the solution identifies C as the correct option and repeats this final order, we take the answer from the solution.

Therefore, the correct option is C.

Common mistakes

  • A common mistake is to rank the compounds directly by the magnitude of electron gain enthalpy without following the rule stated in the solution. This is wrong because the provided solution uses the relative difference to infer ionic character. Follow the ordering given by the solution conclusion.

  • Another mistake is to confuse more negative electron gain enthalpy with more ionic character automatically. In the extracted solution, the stated trend is that the less negative electron gain enthalpy here corresponds to greater ionic character with E. Use that stated trend consistently.

  • Students may stop after arranging D, C, A, B from least negative to most negative and then map it incorrectly to the compound order. The question asks about ED, EC, EB, EA, so the final order must be written in terms of compounds, not isolated elements.

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