Midterm question

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705170809
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Midterm question

Postby 705170809 » Tue Nov 20, 2018 3:13 pm

On the midterm, there was a question that asked for the bond lengths of NO2-. I got the structure correct, but can someone tell me how to find the bond lengths?

Meachelle_Lum_1I
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Re: Midterm question

Postby Meachelle_Lum_1I » Tue Nov 20, 2018 3:15 pm

For this question, when finding bond lengths you would look at the average of the two since resonance is the blending of structures. Thus, you would take the average of 140pm and 120pm to get 130pm as the bond length.

Kathryn 1F
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Re: Midterm question

Postby Kathryn 1F » Tue Nov 20, 2018 3:16 pm

I think it is sufficient to say that because of the resonance,
120pm<the N-O bond lengths<140pm.
The resonance causes the bond lengths to be longer than a double bond, but shorter than a single bond.

Kassidy Tran 1E
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Re: Midterm question

Postby Kassidy Tran 1E » Tue Nov 20, 2018 3:28 pm

Due to the resonance structures, the average of the bond lengths of the different structures should have blended together, so you estimate the bond length between 120 and 140, and that's how you get around 130.

Megan Gianna Uy 3L
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Joined: Fri Sep 28, 2018 12:26 am

Re: Midterm question

Postby Megan Gianna Uy 3L » Tue Nov 20, 2018 5:21 pm

Since resonance is the blending of structures, each N-O bond is an average of the double and single bond shown on the lewis structure. Therefore you would take the average of the two bonds. (140pm+120pm)/2 = 130pm

Nicoline Breytenbach 3D
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Re: Midterm question

Postby Nicoline Breytenbach 3D » Tue Nov 20, 2018 6:20 pm

You could either take the average, or simply say less than 140 but more than 120 pm. Both were taken as correct answers

aisteles1G
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Re: Midterm question

Postby aisteles1G » Tue Nov 20, 2018 6:22 pm

Did midterm scores come out? I still am not able to see mine on MyUCLA, how do you know which ones you got correct?

Sarah_Kang_2K
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Joined: Fri Sep 28, 2018 12:23 am

Re: Midterm question

Postby Sarah_Kang_2K » Tue Nov 20, 2018 11:39 pm

They passed the midterms back after lecture last Wednesday.

SydBenedict2H
Posts: 60
Joined: Wed Nov 08, 2017 3:00 am

Re: Midterm question

Postby SydBenedict2H » Tue Nov 27, 2018 4:20 pm

If you didn't get your midterm after lecture last week, go to your TA and they should have it. When your TA graded it they did a pretty good job of explaining what you got wrong and can explain why you got things wrong.


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