To determine how the equilibrium of the reaction is affected by adding NH3, we need to consider Le Chatelier's principle. According to this principle, when a system at equilibrium is subjected to a change, the system will adjust to minimize the effect of that change and restore equilibrium.
In this case, adding NH3 would increase the concentration of NH3 in the reaction mixture. By increasing the concentration of one of the reactants (NH3), we disrupt the equilibrium balance.
To determine the direction in which the equilibrium will shift, we compare the initial concentrations with the reaction's equilibrium constant, K.
If Q (the reaction quotient, calculated by dividing the molar concentrations of the products by the molar concentrations of the reactants) is larger than K, it means that there is an excess of products, and the reaction will shift in the reverse direction to form more reactants.
However, if Q is smaller than K, it means that there is a deficiency of products, and the reaction will shift in the forward direction to form more products.
Now, let's analyze the possible answers:
A. Increasing the amount of NH3 will make Q larger than K. A net reaction occurs in the direction to reduce NH3, or the reverse reaction.
B. Increasing the amount of NH3 will make Q smaller than K. A net reaction occurs in the direction to increase NH3, or the forward reaction.
C. Increasing the amount of NH3 will make Q larger than K. A net reaction occurs in the direction to increase NH3, or the forward reaction.
D. Increasing the amount of NH3 will make Q smaller than K. A net reaction occurs in the direction to reduce NH3, or the reverse reaction.
When we add NH3, we increase its concentration, which will affect Q. Since Q will become larger than K, the reaction will shift to reduce NH3 and favor the reverse reaction, forming more N2 and H2. So, the correct answer is D.
Therefore, the correct option is D. Increasing the amount of NH3 will make Q smaller than K. A net reaction occurs in the direction to reduce NH3, or the reverse reaction.