Final answer:
When equal volumes of 0.0800 M NH₃ and 0.0400 M HCl are mixed together, the equilibrium concentrations of NH₃ and NH₄+ are both 0.0800 M.
Step-by-step explanation:
When equal volumes of 0.0800 M NH₃ and 0.0400 M HCl are mixed together, a reaction occurs, resulting in the formation of NH₄+ and Cl- ions. In this reaction, the NH₃ acts as a base while the HCl acts as an acid.
To determine the concentrations of NH₃ and NH₄+, we can use the equilibrium constant, Keq, which is given as 4.0. The stoichiometry of the reaction indicates that for every one NH₃ molecule that reacts, one NH₄+ ion is formed.
Since the initial concentration of NH₃ is 0.0800 M and the initial concentration of HCl is 0.0400 M, the equilibrium concentration of NH₃ is also 0.0800 M, and the equilibrium concentration of NH₄+ is 0.0800 M as well.