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JEE Main 20244 AprilMorning Shift
Exam
JEE Main
Year
2024
Date
4 April
Shift
Morning Shift
Subject
Chemistry
Chapter
Thermodynamics (C)

JEE Main 2024 · 4 April · Morning Shift · Chemistry · Thermodynamics (C)

The enthalpy of formation of ethane ( (C_ 2 H_ 6 )) from ethylene...

The enthalpy of formation of ethane ((C2H6))from\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)) fromethylene by addition of hydrogen where the bond-energies of (\mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{C}, C=C\mathrm{C}=\mathrm{C}, \mathrm{H}-\mathrm{H} are (414 \mathrm{~kJ},347347\mathrm{~kJ},,615  kJand\mathrm{~kJ} and(435 \mathrm{~kJ} respectively is (\qquad) (kJ\mathrm{kJ}

Correct answer

125

Step-by-step solution

C2H4( g)+H2( g)→C2H6( g)ΔH=BE(C=C)+4BE(C−H)+BE(H−H)−BE(C−C)−6BE(C−H)ΔH=BE(C=C)+BE(H−H)−BE(C−C)−2BE(C−H)=615+435−347−2×414=−125 kJ\begin{aligned} & \mathrm{C}_2 \mathrm{H}_4(\mathrm{~g})+\mathrm{H}_2(\mathrm{~g}) \rightarrow \mathrm{C}_2 \mathrm{H}_6(\mathrm{~g}) \\ & \Delta \mathrm{H}=\mathrm{BE}(\mathrm{C}=\mathrm{C})+4 \mathrm{BE}(\mathrm{C}-\mathrm{H})+\mathrm{BE}(\mathrm{H}-\mathrm{H}) \\ & -\mathrm{BE}(\mathrm{C}-\mathrm{C})-6 \mathrm{BE}(\mathrm{C}-\mathrm{H}) \\ & \Delta \mathrm{H}=\mathrm{BE}(\mathrm{C}=\mathrm{C})+\mathrm{BE}(\mathrm{H}-\mathrm{H})-\mathrm{BE}(\mathrm{C}-\mathrm{C}) \\ & -2 \mathrm{BE}(\mathrm{C}-\mathrm{H}) \\ & =615+435-347-2 \times 414 \\ & =-125 \mathrm{~kJ}\end{aligned}
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