AAMC Test 11 Chemistry Question

[msmitra]

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I have a question about item 7 on the AAMC test 11.

Which single bond in nitroglycerin is the shortest?

Why is the answer a. O-H?

I dont understand what should make me choose this over C-C, or C-O. Oxygen is more electronegative thus wouldn't it pull carbon closer, making that single bond shorter than the C-H bond? How is the C-H bond harder to break?

 

[Ssina]

I think you mean C-H in the bolded

I personally looked at the bond energy data provided in the passage (right below the table) and CH has the highest bond energy so requires the most amount of energy to be broken..... hence it's a smaller bond vs. others.

but if not using those data, you have consider other stuff like electronegativity of atoms.... in N-O each pull on the electron density so the bond is longer (as at extreme cases this leads to ions so no bonds e.g. Na----OH)... but overall the more S character the stronger and smaller the bond... and C is a sp3 bonding with s orbital of H (so it's stronger) vs. sp3 to sp3 for C-C or C-O

 

[MedPR]

I think you mean C-H in the bolded

I personally looked at the bond energy data provided in the passage (right below the table) and CH has the highest bond energy so requires the most amount of energy to be broken..... hence it's a smaller bond vs. others.

but if not using those data, you have consider other stuff like electronegativity of atoms.... in N-O each pull on the electron density so the bond is longer (as at extreme cases this leads to ions so no bonds e.g. Na----OH)... but overall the more S character the stronger and smaller the bond... and C is a sp3 bonding with s orbital of H (so it's stronger) vs. sp3 to sp3 for C-C or C-O

I agree that CH bond is shorter than the OH bond. OH bonds are significantly weaker, and thus longer.

 

[MedPR]

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It turns out that many students who were pressured into buying the same day as the presentations did NOT get those results.

If you were pressured into buying a D l T Review based upon their promises, and did not pass or get above a 230, please visit our web page and list your complaint.

Once enough names are collected a legal firm will begin working on litigation which could get you a full refund.

Lol.
Fail.

 

[mcloaf]

Last year the program D l T came to my medical schools promising 98% pass rates and average scores above 230 on the USMLE.

It turns out that many students who were pressured into buying the same day as the presentations did NOT get those results.

If you were pressured into buying a D l T Review based upon their promises, and did not pass or get above a 230, please visit our web page and list your complaint.

Once enough names are collected a legal firm will begin working on litigation which could get you a full refund.

To be honest, unless they guaranteed you such scores, I'm not sure how successful you're going to be.

Either way, this forum isn't the place to post about it.

 

[msmitra]

Hey, Thanks Ssina! I that makes more sense. Since we are comparing single bonds, I should just consider bond dissociation energy to determine which one is the shortest. (And N-O wouldn't count in the comparison because it is has partial double bond character seen in resonance).