AAMC FL 3, C/P, Q9

[mariposas905]

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I did not know how to pick btwn. A and D...I thought boiling points were also an indicator of stability (higher boiling point, more stability). How do you know it's D and not A?

 

[Doogie.Howser]

The high or low boiling point doesn't tell you the stability of the compound, but it allows you to infer about the high or low amount of intermolecular forces, respectively.

When you take a compound and perform a combustion reaction, heat is released. The amount of heat released is deltaH, which is a thermodynamic property that informs you about the stability of the compound. A larger deltaH means more heat was released. These deltaH values from performing a combustion reaction tell you about the stability differences of isomers.

 

[SonhosDaVida]

I agree with doogie

 

[mariposas905]

The high or low boiling point doesn't tell you the stability of the compound, but it allows you to infer about the high or low amount of intermolecular forces, respectively.

When you take a compound and perform a combustion reaction, heat is released. The amount of heat released is deltaH, which is a thermodynamic property that informs you about the stability of the compound. A larger deltaH means more heat was released. These deltaH values from performing a combustion reaction tell you about the stability differences of isomers.

Thanks! and more heat released means that compound is more stable?

 

[Doogie.Howser]

Yes. If heat is released - exothermic reaction - then the products are more stable than the reactants.

 

[AdaptPrep]

"and more heat released means that compound is more stable?"

If you are comparing the heat of combustion and the amount of heat given off for different isomers, the HIGHER heat of combustion implies LOWER stability. For example, the cis isomer has a higher heat of combustion than the trans isomer, because it is less stable (you had to put more energy into forming the cis isomer since it is not as stable). If you are forming something stable, it does not take as much energy to form it when compared to forming something less stable. Therefore, the stable compound will release less heat when combusted.

 

[prehealthboi]

The high or low boiling point doesn't tell you the stability of the compound, but it allows you to infer about the high or low amount of intermolecular forces, respectively.

When you take a compound and perform a combustion reaction, heat is released. The amount of heat released is deltaH, which is a thermodynamic property that informs you about the stability of the compound. A larger deltaH means more heat was released. These deltaH values from performing a combustion reaction tell you about the stability differences of isomers.

I think you mean a more negative ΔH means more heat was released. If it's a large/positive value, it's an endothermic reaction. Or were you talking about the absolute value of ΔH?