Method 2

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Valeria Viera 1B
Posts: 60
Joined: Fri Apr 06, 2018 11:05 am

Method 2

Postby Valeria Viera 1B » Fri Jan 25, 2019 9:11 pm

Under method two- additional comments from the notes it says “ 2) bond enthalpies of diatomic molecules are accurate (measured for those molecules)” what does this mean? And enthalpies of diatomic molecules are more accurate as opposed to what, exactly?

Thank you!

Joon Chang 2F
Posts: 59
Joined: Fri Sep 28, 2018 12:25 am

Re: Method 2

Postby Joon Chang 2F » Fri Jan 25, 2019 10:03 pm

Bond enthalpies of diatomic molecules are able to be measured because they are only between two types of atoms, whereas enthalpies of other bonds are averages from different molecules. The bond enthalpy of the diatomic molecule H2 is +436 kJ. This enthalpy is able to be measured consistently because it is between the same atoms and the bond will most likely be the same each time. The bond enthalpy between O-H however, differs based on what molecule it is in. The O-H bond enthalpy in water is slightly different than that of methanol, so the O-H bond enthalpy is the mean bond enthalpy taken from different molecules.

Iris Bai 2K
Posts: 60
Joined: Fri Sep 28, 2018 12:18 am

Re: Method 2

Postby Iris Bai 2K » Fri Jan 25, 2019 11:09 pm

Because diatomic molecules are not bonded to anything else, the bond enthalpies measured for those bonds are the most accurate. If that same bond occurs in a larger molecule, the bond enthalpy for the same bond in the larger molecule may be slightly different.

taryn_baldus2E
Posts: 62
Joined: Fri Sep 28, 2018 12:24 am

Re: Method 2

Postby taryn_baldus2E » Sat Jan 26, 2019 9:12 am

Furthermore, since the bond enthalpy is different for each molecule, it is the least accurate of the three methods.


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