Change in Enthaply and Activation Energy

In summary, the conversation discusses whether the activation energy for an exothermic reaction in the forward direction can be less than the enthalpy change. The book suggests that this is possible, possibly referring to the magnitude of the activation energy rather than its actual value. The conversation ends with an agreement that this is the most likely interpretation.
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student34
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Homework Statement



For a reaction that is exothermic in the forward direction, can the activation energy Ea(fwd) ever be less than the enthalpy change?

Homework Equations



Endothermic equation: Ea(rev) = Ea(fwd) - deltarH

The Attempt at a Solution


[/B]
The answer in the book has "yes", but I don't know how this can be true.

Since it's an exothermic reaction, deltarH is negative. And as far as I know, the forward activation energy must be positive. Is it possible that the book meant magnitude? If so, then I could understand why they gave that answer.
 
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  • #2
student34 said:
Is it possible that the book meant magnitude?

That would be my understanding.
 
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Borek said:
That would be my understanding.
:smile: Thanks!
 

1. What is the definition of enthalpy?

Enthalpy is a thermodynamic property that measures the total energy of a system, including the internal energy and the work required to change the system's volume at constant pressure.

2. How does enthalpy change during a chemical reaction?

Enthalpy can either increase or decrease during a chemical reaction, depending on whether the reaction is exothermic or endothermic. Exothermic reactions release energy, causing a decrease in enthalpy, while endothermic reactions absorb energy, causing an increase in enthalpy.

3. What is activation energy?

Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is the energy needed to break the bonds of the reactants and initiate the reaction.

4. How does activation energy affect the rate of a reaction?

A higher activation energy typically results in a slower reaction rate, as it requires more energy for the reactants to reach the transition state and form products. A lower activation energy leads to a faster reaction rate, as less energy is needed for the reaction to occur.

5. Can enthalpy and activation energy be changed?

Enthalpy and activation energy are inherent properties of a chemical reaction and cannot be changed. However, the rate of a reaction can be altered by changing factors such as temperature, concentration, and the use of a catalyst, which can affect the enthalpy and activation energy of the reaction.

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