AAMC 10 Biology Passage II, Item 9... energy density???

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MedGrl@2022

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So I choose the only answer that made sense... but I still have no idea how the answer correlates with energy density... or what energy density exactly is....

What bonding accounts for the expected increase in energy density of solid nitrogen as compared to methanol?

A. Solid nitrogen contains covalent and ionic bonds; methanol contains only weak ionic bonds.
B. Solid nitrogen contains covalent and ionic bonds; methanol has covalent bonds within each molecule and weak van der Waal's interactions between molecules.
C. Solid nitrogen contains only covalent bonds; methanol contains only weak ionic bonds.
D. Solid nitrogen contains only covalent bonds; methanol has covalent bonds within each molecule and weak intermolecular interactions.

So obviously, it is D but what does this have to do with energy density? Couldn't methanol have higher energy density as it has intermolecular forces as well as covalent bonds?

Thank you for your help!

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So I choose the only answer that made sense... but I still have no idea how the answer correlates with energy density... or what energy density exactly is....

What bonding accounts for the expected increase in energy density of solid nitrogen as compared to methanol?

A. Solid nitrogen contains covalent and ionic bonds; methanol contains only weak ionic bonds.
B. Solid nitrogen contains covalent and ionic bonds; methanol has covalent bonds within each molecule and weak van der Waal's interactions between molecules.
C. Solid nitrogen contains only covalent bonds; methanol contains only weak ionic bonds.
D. Solid nitrogen contains only covalent bonds; methanol has covalent bonds within each molecule and weak intermolecular interactions.

So obviously, it is D but what does this have to do with energy density? Couldn't methanol have higher energy density as it has intermolecular forces as well as covalent bonds?

Thank you for your help!

This is actually from the Physical Sciences section... anyone have any ideas?
 
Well, energy density would be density in terms of energy per volume rather than mass per volume. In this case, you are considering the energy of bonds for these two molecules. As I see it, solid nitrogen would be much more compact and contain many more atoms/bonds in a given volume than methanol (liquid). I don't know much about the solid crystal of nitrogen (wikipedia says it's hexagonal?), but I would imagine that they would pack as well as methanol, if not better, and the energy in a covalent bond would be much greater than the energy in intermolecular forces(/bonds).

To be honest, for this question, I used POE, but further speculation would necessitate more information on both molecules.
 
Hello,
There are two important points to correctly answer and understand this question:
1) Chemical bonds are so much stronger than inter-molecular forces.
2) Solid molecules are too much close to each other, compared to liquid.

Then, covalent bonds withing N2 (Solid) are so much greater than any type of intermolecular forces between methanol, including the H-bonds.

So, we will put the intermolecular forces aside, and compare the chemical bonds only (within the molecule).

Although CH3OH has polar covalent bond in between C & OH, there is triple covalent bonds between the 2 nitrogen atoms. Moreover, N2 molecules are well packed in small volume, so their energy density is so much higher than that of the methanol liquid.
 
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