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brake4country
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Homework Statement
Given that the bond energy of hydrogen-hydrogen bonds is 436 KJ/mol, that of hydrogen-oxygen bonds is 464 KJ/mol, and those in oxygen molecules 496 KJ/mol, what is the approximate heat of reaction for 2H2 + O2→2H2O
Homework Equations
Hproducts-Hreactants
The Attempt at a Solution
So, I understand that heats of reaction involving hydrogen gas and oxygen gas to liquid water is exothermic, so my answer must be negative. My book gives and answer of -488 KJ/mol but I keep ending up with -440 KJ/mol:
2(464) - [2(436) + 496] = -440 KJ/mol.
Calculation error? I went over the numbers twice. Thanks!