JEE Main 2025 · ChemistryNumerical answerNumerical valueMediumCalculation

JEE Main 3 April 2025, Shift 1, Chemistry Q71

Question 71 of 75 in this shift, Chemistry question 21 of 25, Section B.

Given :

\Delta H^{\ominus}_{sub}

[C (graphite)] = 710 kJ mol

^{-1}

\Delta_{C-H}H^{\ominus}

= 414 kJ mol

^{-1}

\Delta_{H-H}H^{\ominus}

= 436 kJ mol

^{-1}

\Delta_{C=C}H^{\ominus}

= 611 kJ mol

^{-1}

The

\Delta H_f^{\ominus}

for

\mathrm{CH_2 = CH_2}

is ______ kJ mol

^{-1}

(nearest integer value)

Official answer

NTA final key.

Chapter: Thermodynamics (Chemistry)
Topic: Enthalpy and Hess's Law
Idea tested: Bond Enthalpy Calculations

Same idea in other shifts

Asked 5× in all

4 Apr 2024, Shift 1 · Q83The enthalpy of formation of ethane ( $\mathrm{C_2H_6}$ ) from ethylene by addition of hydrogen where the bond-energies of C $-$ H, C $-$ C,…EasyNumerical value
13 Apr 2023, Shift 1 · Q83 $\mathrm{A_2}+\mathrm{B_2}\rightarrow 2\mathrm{AB}$ . $\Delta H_f^0 = -200\ \mathrm{kJ\ mol^{-1}}$ AB, $\mathrm{A_2}$ and $\mathrm{B_2}$ …MediumNumerical value
26 Feb 2021, Shift 2 · Q54The average S $-$ F bond energy in kJ $\mathrm{mol^{-1}}$ of $\mathrm{SF_6}$ is __________. (Rounded off to the nearest integer) [Given :…MediumNumerical value
18 Mar 2021, Shift 1 · Q53For the reaction $\mathrm{C_2H_6 \rightarrow C_2H_4 + H_2}$ the reaction enthalpy $\Delta_rH =$ __________ kJ mol $^{-1}$ . (Round off to…EasyNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.