Consider the reaction of chloromethane with OH- in aque- ous solution: CH Cl1aq2 + OH-1aq2 ∆kf CH OH1aq2 + Cl-1aq2 At 25 °C, the rate constant for the forward reaction is 6 * 10-6 M-1 s-1, and the equilibrium constant Kc is 1 * 1016. Calculate the rate constant for the reverse reac- tion at 25 °C.
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Identify the given values: the rate constant for the forward reaction \( k_f = 6 \times 10^{-6} \text{ M}^{-1} \text{s}^{-1} \) and the equilibrium constant \( K_c = 1 \times 10^{16} \).
Recall the relationship between the equilibrium constant \( K_c \), the rate constant for the forward reaction \( k_f \), and the rate constant for the reverse reaction \( k_r \): \( K_c = \frac{k_f}{k_r} \).
Rearrange the equation to solve for the rate constant of the reverse reaction \( k_r \): \( k_r = \frac{k_f}{K_c} \).
Substitute the known values into the equation: \( k_r = \frac{6 \times 10^{-6} \text{ M}^{-1} \text{s}^{-1}}{1 \times 10^{16}} \).
Simplify the expression to find the value of \( k_r \).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Rate Constant (k)
The rate constant (k) is a proportionality factor in the rate law of a chemical reaction, indicating the speed at which a reaction proceeds. It is specific to a particular reaction at a given temperature and is influenced by factors such as concentration and temperature. In this case, the forward rate constant is given, which is essential for calculating the reverse rate constant.
The equilibrium constant (Kc) is a dimensionless value that expresses the ratio of the concentrations of products to reactants at equilibrium for a reversible reaction. It provides insight into the extent of the reaction and is related to the rate constants of the forward and reverse reactions. For the given reaction, Kc is used to derive the reverse rate constant using the relationship Kc = kf / kr.
Relationship Between Rate Constants and Equilibrium Constant
The relationship between the rate constants of the forward (kf) and reverse (kr) reactions and the equilibrium constant (Kc) is given by the equation Kc = kf / kr. This relationship allows us to calculate the reverse rate constant if the forward rate constant and the equilibrium constant are known. Understanding this relationship is crucial for solving the problem presented.
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