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Ch.15 - Chemical Equilibrium
Chapter 15, Problem 1a

(a) Based on the following energy profile, predict whether kf > kr or kf < kr. [Section 15.1]

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Identify the activation energies for the forward (Ea_f) and reverse (Ea_r) reactions from the energy profile diagram.
Compare the magnitudes of Ea_f and Ea_r. The reaction with the lower activation energy generally has a higher rate constant.
If Ea_f is less than Ea_r, then the forward rate constant k_f is greater than the reverse rate constant k_r (k_f > k_r).
If Ea_f is greater than Ea_r, then the forward rate constant k_f is less than the reverse rate constant k_r (k_f < k_r).
Predict the relationship between k_f and k_r based on the comparison of their respective activation energies.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Reaction Rate Constants (k_f and k_r)

In chemical kinetics, k_f represents the rate constant for the forward reaction, while k_r denotes the rate constant for the reverse reaction. The relative magnitudes of these constants indicate the favorability of the reaction direction. If k_f is greater than k_r, the forward reaction is favored, leading to a higher concentration of products at equilibrium.
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Energy Profile Diagrams

Energy profile diagrams illustrate the energy changes during a chemical reaction, showing the energy of reactants, products, and the activation energy required for the reaction to proceed. The shape of the diagram can indicate whether the forward or reverse reaction is more energetically favorable, which directly influences the values of k_f and k_r.
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Equilibrium and Le Chatelier's Principle

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. Le Chatelier's Principle states that if a system at equilibrium is disturbed, it will shift in a direction that counteracts the disturbance. Understanding this principle helps predict how changes in conditions affect k_f and k_r.
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