# Calculate resonance energy

1. Oct 16, 2012

### utkarshakash

1. The problem statement, all variables and given/known data
Determine the resonance energy of gaseous benzene from the following data
$ΔH^{o}_{diss}(H,g)=435.9kJmol^{-1}, ΔH^{o}_{sub} C_{graphite}=718.4kJmol^{-1} ΔH^{o}_{f} Benzene(g)=82.9kJmol^{-1}$

$ε_{C-H}=416.3kJmol^{-1},ε_{C-C}=331.4kJmol^{-1},ε_{C=C}=591.3kJmol^{-1}$

2. Relevant equations

3. The attempt at a solution
I have the following reaction

$6C+3H_{2} \rightarrow C_{6}H_{6}$

To calculate ΔH
$\left[ 6 \times ΔH^{o}_{sub} C_{graphite} + 6 \times ΔH^{o}_{diss}(H,g) \right] - \left[ 6 \times ε_{C-H} + 3 \times ε_{C-C} + 3 \times ε_{C=C} \right]$

Now resonance energy can be calculated by
$R.E. = ΔH_{observed}-ΔH_{calculated}$

Substituting the values does not give me the correct answer.

2. Oct 16, 2012

### AGNuke

To calculate ΔH
$\left[ 6 \times ΔH^{o}_{sub} C_{graphite} + 3 \times ΔH^{o}_{diss}(H,g) \right] - \left[ 6 \times ε_{C-H} + 3 \times ε_{C-C} + 3 \times ε_{C=C} \right]$

I believe you are dissociating 3 H-H bonds.

3. Oct 16, 2012

### utkarshakash

OK So I got my answer(not exactly but very close) but the answer given in my book is positive unlike mine.

4. Oct 17, 2012

### AGNuke

Its because you did mistake there again.

R.E. = H(calculated) - H(observed)

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