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# ΔH [Reactants] - ΔH [ Products] Watch

1. Benzene is used as a petrol additive to reduce knocking.

I am trying to find the ΔH Combustion of benzene, i have not been told what it is burning in so i will presume oxygen.

Is this the correct formula: ΔH [Reactants] - [ Products] ?

C6H6 + 15 O = 6 C02 + 3 H20

ΔH [(1)(C6H6) + (15)(O)] - ΔH[(6)(CO2) + (3) (H20)]

ΔH [(1)(48.95) + (15)(0)] - ΔH[(6)(−393.509) + (3) (−285.830)]

Can somebody show me how to solve this.

Thankyou.
2. ΔH (Products)- ΔH (Reactants) = ΔH
15 O should be 15/2 O2.

So the Enthalpy of Combustion of 1 mole of benzene is also equal to 6(ΔHc (C)graphite) + ΔHf (H20)

I assume the values you use are the ones obtained under standard conditions? ... in which case you should use:
ΔH (Products)- ΔH (Reactants) = ΔH

Remember : always products - reactants.
3. (Original post by Savvy Sage)
ΔH (Products)- ΔH (Reactants) = ΔH
15 O should be 15/2 O2.

So the Enthalpy of Combustion of 1 mole of benzene is also equal to 6(ΔHc (C)graphite) + ΔHf (H20)

I assume the values you use are the ones obtained under standard conditions? ... in which case you should use:
ΔH (Products)- ΔH (Reactants) = ΔH

Remember : always products - reactants.
Yes i used a standard conditions list, i found one on wikipedia. http://en.wikipedia.org/wiki/Standar...8data_table%29

And thank you very much for the clarification, appreciate it.

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Updated: April 8, 2013
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