If at 298K, the bond energies of C−H,C−C,C=C and H−H bonds are 414, 347, 615 and 435kJ/mol respectively, then the value of enthalpy change for the reaction H2C=CH2(g)+H2(g)→H3C−CH3(g) at 298K will be:
A
−250kJ
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B
+125kJ
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C
−125kJ
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D
+250kJ
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Solution
The correct option is C−125kJ Given that the bond energies of C−H,C−C,C=C and H−H bonds are 414,347,615 and 435 kJ/mol respectively at 298 K.
We need to find the enthalpy change at 298 K for the following reaction:
H2C=CH2(g)+H2(g)→H3C−CH3(g)
ΔH= Bond energy for reactants - Bond energy for products