December 24, 2024, 07:40:43 AM
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Topic: Relations between Kinetic and Potential Energy: Adiabitic Bomb Calorimeter  (Read 3505 times)

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Offline Il Divo

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So I'm having some trouble grasping the basics between kinetic and potential energies, with respect to chemical reactions and how the two are converted into each other.

Specifically with regard to this equation:

Um = Um (0) + 3/2RT

which deals with the internal energy of a monoatomic ideal gas.

1) So energy is, in effect, another way of describing the stability of a system. More energy in general indicates a greater reactivity in order for the system to achieve a state of greater stability (lower energy). The first law tells us that energy cannot be created or destroyed, but only changed from one form to another. This leads to my first question regarding the relationship between potential energy and intermolecular forces: in ionic bonding, we say that potential energy decreases as a cation and anion come closer together, resulting in greater stability between the two and decreasing the potential energy of the system. However, following the 1st law, where does this potential energy go as the two come closer in contact?

2) With regard to the above equation, does the first term, Um (0), refer to the potential energy possessed by a compound? I ask because at T=0, the system would have no kinetic energy, hence the first term would have to be completely independent of T. And if so, is it a safe assumption that a compound which does not undergo any chemical reactions will have a constant potential energy, since it is assumed that the molecules are not interacting with each other to any great extent (ideal)?

3) My book makes mention of an adiabatic bomb calorimeter, which would be a system where the volume is unable to change (w=0) and no heat may enter or exist the system (q=0). Under these restrictions, we can determine the heat capacity of the calorimeter by observing a chemical reaction. Endothermic indicates that the reaction requires heat to proceed and exothermic is vice-versa. So if the reaction is endothermic, requiring energy, would this come in the form of using the molecule's kinetic energy, in order to raise the potential energy to a higher state, but lowering the speed overall of each molecule?

Much appreciated and sorry for all the text. 

Offline curiouscat

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Endothermic indicates that the reaction requires heat to proceed and exothermic is vice-versa. So if the reaction is endothermic, requiring energy, would this come in the form of using the molecule's kinetic energy, in order to raise the potential energy to a higher state, but lowering the speed overall of each molecule?


Yes. The Temp. of the mix would decrease. Molecular speed reduction manifests itself as specific  heat.

Offline Il Divo

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Endothermic indicates that the reaction requires heat to proceed and exothermic is vice-versa. So if the reaction is endothermic, requiring energy, would this come in the form of using the molecule's kinetic energy, in order to raise the potential energy to a higher state, but lowering the speed overall of each molecule?


Yes. The Temp. of the mix would decrease. Molecular speed reduction manifests itself as specific  heat.

Apologies for the delayed response, but very much appreciated! Alot of this stuff can be non-intuitive, so it's always good to have someone double-check my reasoning.

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