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 rate of the forward reaction equals the rate of the reverse reaction.
The concentrations of reactants and products are constant, but not necessarily equal.
Evaluate each statement based on the definition of dynamic equilibrium.
The correct statement is: The rate of the forward reaction equals the rate of the reverse reaction. T h e r a t e o f t h e f or w a r d re a c t i o n e q u a l s t h e r a t e o f t h e re v erse re a c t i o n .
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 identify the true statement about this equilibrium system from the given options.
Key Concepts Dynamic equilibrium is a state where the rate of the forward reaction equals the rate of the reverse reaction. This means that while the reaction is still occurring in both directions, the net change in concentrations of reactants and products is zero. The concentrations of reactants and products are constant, but not necessarily equal.
Analyzing the Statements Let's analyze each statement:
"The concentration of N H 3 is greater than the concentration of N 2 ." This statement is not necessarily true. At equilibrium, the concentrations of reactants and products are constant, but their relative amounts depend on the equilibrium constant and initial conditions. It's possible for [N_2]"> [ N H 3 ] > [ N 2 ] , [ N H 3 ] < [ N 2 ] , or [ N H 3 ] = [ N 2 ] .
"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. If the rate of the forward reaction were greater than the rate of the reverse reaction, the system would not be at equilibrium; the concentration of products would increase, and the concentration of reactants would decrease until equilibrium is reached.
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 true statement for the equilibrium system is that the rate of the forward reaction equals the rate of the reverse reaction. This is a fundamental principle of dynamic equilibrium in chemical reactions. Therefore, option B is correct.
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