Having trouble with bond enthalpies of Q1B on Midterm

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Suk Jin Song 3L
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Joined: Tue Nov 17, 2015 3:00 am

Having trouble with bond enthalpies of Q1B on Midterm

Postby Suk Jin Song 3L » Sun Feb 21, 2016 10:37 pm

For Question number 1B of the midterm, the answer key state that a C-C bond was broken but I cannot find that info on the figures.
I can see C-O and C-H bonds breaking and O-H and C-C bonds forming but not C-C bond breaking.

Can someone tell me how I can interpret that info based on the figure for the question?

A very very simple question that I fear there is a very easy answer to. But still wanted a clear answer.

Monica Hana 2G
Posts: 19
Joined: Fri Sep 25, 2015 3:00 am

Re: Having trouble with bond enthalpies of Q1B on Midterm

Postby Monica Hana 2G » Mon Feb 22, 2016 12:27 am

For the compound in the reactants,
In Carbon (1), there is a C=O, C-O, and C1-C2 bond.
In Carbon (2), there is a C-H, C-O, and C2-C3 bond. (As well as the C1-C2 bond, which we've already accounted for)
In Carbon (3), there is a C-O, and 2 C-H bonds. (As well as the C2-C3 bond, which we've already accounted for)
There is also an O-H bond, and 4 O-P bonds.

For the compounds in the products,
In Carbon (1), there is a C=O, C-O, and C1-C2 bond.
In Carbon (2), there is a C-O and C2=C3 bond. (As well as the C1-C2 bond, which we've already accounted for)
In Carbon (3), there are 2 C-H bonds. (As well as the C2=C3 bond, which we've already accounted for)
There is also 4 O-P bonds and 2O-H bonds.

What I did from there is cross out all of the bonds that were repeated in both the products and reactants. I wrote down any bonds in the reactants that weren't accounted for in the products in the list of "bonds broken" and I did the opposite for the list of "bonds formed." Then I found the bond enthalpies by using the values from the table and multiplying each value by the number of those bonds.

Does that make sense?


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