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Bond Enthalpy Accuracy

Posted: Fri Jan 24, 2020 2:32 pm
by Shannon Asay 1C
Why is using bond enthalpies the least accurate method for calculating delta H?

Re: Bond Enthalpy Accuracy

Posted: Fri Jan 24, 2020 2:55 pm
by Alexis Webb 2B
I think it is because the bond enthalpies are calculated as averages from many different molecules, so they are not the most accurate.

Re: Bond Enthalpy Accuracy

Posted: Fri Jan 24, 2020 3:04 pm
by Ellen Amico 2L
Bond enthalpies are for breaking bonds in gases, so you need to add in the enthalpy of phases changes for reactants/products that are liquid or solid. Additionally, they're averages from many different molecules, which makes them less accurate. Using Hess's Law or the standard enthalpies would be a better method.

Re: Bond Enthalpy Accuracy

Posted: Fri Jan 24, 2020 3:41 pm
by Sanjana Borle 2K
Bond enthalpies are only accurate with diatomic molecules with atoms of the same type, otherwise it is not so accurate since the enthalpy is calculated using averages.

Re: Bond Enthalpy Accuracy

Posted: Fri Jan 24, 2020 3:55 pm
by Asha Agarwal 1E
Bond enthalpies of diatomic molecules are completely accurate, but for all other bonds formed the bond enthalpy given is an average of all different bonds of that nature that occurred instead of the actual value for that specific bond or reaction, so there is some error, making it the least accurate.

Re: Bond Enthalpy Accuracy

Posted: Fri Jan 24, 2020 5:57 pm
by Leyna Dang 2H
I'm not sure but I think it has to do with the fact that the bond enthalpies of all molecules other than diatoms are averages. Since the averages are given and not the actual values, they aren't as accurate.

Re: Bond Enthalpy Accuracy

Posted: Fri Jan 24, 2020 6:30 pm
by Daria MacAuslan 1H
The enthalpy of bonds is calculated by taking the averages of many different molecules, so you cant get a perfectly accurate and specific value for this. For diatomic molecules, however, it is accurate.