Key Idea Enthalpy of reaction =∑BEReactants −∑BEProducts For reaction, 
ΔHr=[4×BE(C−H)+1×BE(C=C)+1×BE(H−H)]−[6×BE(C−H)+1×BE(C−C)]=(4×410.50+1×606.10+1×431.37)−[(6×410.50)+(1×336.49)]=−120.0 kJ mol−1
From the following bond energies : H- H bond energy : 431.37 ~kJ ~mol^-1 C= C bond energy : 606.10 ~kJ ~mol^-1 C - C bond energy : 336.49 ~kJ ~mol^-1…
NEET UG 2009 — Chemistry Physical Chemistry
2009mcqhard
From the following bond energies : H−H bond energy : 431.37 kJ mol−1 C=C bond energy : 606.10 kJ mol−1 C - C bond energy : 336.49 kJ mol−1 C−H bond energy : 410.50 kJ mol−1 Enthalpy for the reaction, 
will be
Official previous-year question
Held on 30 Apr 2009 · Verified 9 Jul 2026.
Options
- A
1523.6 kJ mol−1
- B
−243.6 kJ mol−1
- C
−120.0 kJ mol−1
- D
553.0 kJ mol−1
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