Question

the reaction below is at dynamic equilibrium.
n₂(g) + 3h₂(g)⇌2nh₃(g)
which statement is true for the equilibrium system?
○ the concentration of nh₃ is greater than the concentration of n₂.
○ the concentration of nh₃ equals the concentration of n₂.
○ the rate of the forward reaction equals the rate of the reverse reaction.
○ the rate of the forward reaction is greater than the rate of the reverse reaction.

Explanation:

To determine the true statement for the equilibrium system \( \ce{N_{2}(g) + 3H_{2}(g)\longleftrightarrow 2NH_{3}(g)} \), we recall the definition of dynamic equilibrium: at dynamic equilibrium, the rate of the forward reaction (conversion of reactants to products) is equal to the rate of the reverse reaction (conversion of products to reactants).

• The first option ("The concentration of \( \ce{NH_{3}} \) is greater than the concentration of \( \ce{N_{2}} \)") is not necessarily true. Equilibrium does not imply a specific relationship between the concentrations of products and reactants; it depends on the equilibrium constant and initial conditions.
• The second option ("The concentration of \( \ce{NH_{3}} \) equals the concentration of \( \ce{N_{2}} \)") is also not necessarily true for the same reason as the first option—equilibrium concentrations depend on the reaction's equilibrium constant and initial concentrations, not a fixed equality between specific reactants and products.
• The third option ("The rate of the forward reaction equals the rate of the reverse reaction") matches the definition of dynamic equilibrium.
• The fourth option ("The rate of the forward reaction is greater than the rate of the reverse reaction") is false because, at equilibrium, the forward and reverse reaction rates are equal (if the forward rate were greater, the reaction would still be proceeding in the forward direction and not at equilibrium).

Answer:

The rate of the forward reaction equals the rate of the reverse reaction.