Calculate △Hor for the reaction CH2Cl2(g)→C(g)+2H(g)+2Cl(g).
The average bond enthalpies of C - H and C - Cl bonds are 414kJmol−1 and 330kJmol−1.
A
1488kJmol−1
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B
1468kJmol−1
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C
1478kJmol−1
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D
1498kJmol−1
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Solution
The correct option is A1488kJmol−1 We are given εC−H=414kJmol−1 εC−Cl=330kJmol−1
We know ΔrH=∑(BondEnergy)reactants−∑(BondEnergy)products
Here the bond energy of products won't be taken into account as the products doesn't contain any bonds.
So, △Hr=2εC−H+2εC−Cl
putting the values, =2×414+2×330 =828+660=1488kJ/mol.
hence, △Hr=1488kJ/mol.
Theory:
Determination of enthalpy of reaction: ΔrH=∑(BondEnergy)reactants−∑(BondEnergy)products