The reaction below is at dynamic equilibrium.
[tex]$N_2(g)+3 H_2(g) \longleftrightarrow 2 NH_3(g)$[/tex]
Which statement is true for the equilibrium system?
A. The concentration of [tex]$NH _3$[/tex] is greater than the concentration of [tex]$N _2$[/tex].
B. The rate of the forward reaction equals the rate of the reverse reaction.
C. The rate of the forward reaction is greater than the rate of the reverse reaction.
Answer (2)
Dynamic equilibrium means the forward and reverse reaction rates are equal.
Concentrations of reactants and products are constant, but not necessarily equal.
The rate of the forward reaction equals the rate of the reverse reaction is the correct statement.
Therefore, the correct answer is that the rate of the forward reaction equals the rate of the reverse reaction.
Explanation
Understanding the Problem The problem states that the reaction N 2 ( g ) + 3 H 2 ( g ) ⟷ 2 N H 3 ( g ) is at dynamic equilibrium. We need to determine which of the given statements is true.
Key Concepts At dynamic equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction. This means that reactants are being converted into products at the same rate that products are being converted back into reactants. The concentrations of reactants and products remain constant, but they are not necessarily equal.
Evaluating the Statements Let's evaluate each statement:
The concentration of N H 3 is greater than the concentration of N 2 . This statement is not necessarily true. The concentrations of reactants and products at equilibrium depend on the equilibrium constant, K , and the initial conditions. It is possible for the concentration of N H 3 to be greater than, less than, or equal to the concentration of N 2 at equilibrium.
The rate of the forward reaction equals the rate of the reverse reaction. This statement is true by the definition of dynamic equilibrium.
The rate of the forward reaction is greater than the rate of the reverse reaction. This statement is false because, at equilibrium, the rates are equal.
Conclusion Therefore, the correct statement is: The rate of the forward reaction equals the rate of the reverse reaction.
Examples
Consider a tug-of-war where two teams are pulling on a rope. If the forces exerted by both teams are equal, the rope doesn't move, even though both teams are actively pulling. This is analogous to dynamic equilibrium in a chemical reaction, where the forward and reverse reactions occur at the same rate, resulting in no net change in concentrations.
The correct statement for the equilibrium reaction N 2 ( g ) + 3 H 2 ( g ) ⟷ 2 N H 3 ( g ) is B. The rate of the forward reaction equals the rate of the reverse reaction. This is a fundamental characteristic of dynamic equilibrium in chemical processes.
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