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The statement that it is impossible to calculate the absolute energy at an ambient T seems to be intuitively incorrect, difficult possibly, but not impossible. Since U is a state function the value of U for a given set of conditions is invariable and can be set as an arbitrary zero and changes in U calculated. So all one must do is work in reverse to ...

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There are two factors here to consider. First, the energy released by a given reaction is (partly) due to the difference between the bond strength in the product vs reactant, not the absolute bond strength, unless the reaction involves just breaking a bond and not forming a new one. Second, even if your reaction is just a bond breaking, there are multiple ...

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As porphyrin pointed out, two hydrogen atoms coming together from infinite distance will tend to bond, if the energy of the bond can be dissipated. This is unlike the situation where two magnets click together and stay together (because that interaction hits an absolute minimum, rather than a roller-coaster upswing as in the diagram. Ref 1). Two hydrogen ...

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The bond enthalpy is conventionally the enthalpy change of bond breaking, not of bond forming, in the contrary to formation enthalpy of compounds. This way they are all positive. The consequence is, the order of products and reactants in computation the enthalpy difference has to be switched. So if the summary bond enthalpy of products is higher than of ...

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The $\mathrm{S_N1}$ reaction has two steps i) the formation of carbocation and 2) the formation of product. (image taken from libretexts) In the second step an unstable carbocation reacts with the nucleophile. You are asking why this step has to have an activation energy. You can rationalize that by considering the principle of microscopic reversibility. ...

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Dr. Larry Moran (Professor Emeritus in the Department of Biochemistry at the University of Toronto) has posted an nice article about the Free Energy of ATP Hydrolysis. Accordingly, some important concepts in biochemistry may be widely misunderstood and/or not well described in most textbooks. One of them is the free energy of ATP hydrolysis: The traditional ...

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You're not really wrong: the computer program is apparently expecting a float and not an integer, which is really stupid because the question is about temperature change and not the vagaries of significant figures. Instead of you learning about heat capacity and the relation to temperature change, you're instead learning about significant figures first, and ...

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