Final answer:
Keq includes concentrations of gases and aqueous species at equilibrium, while solids and liquids are omitted because their concentrations remain constant. Q, or Ktrial, represents the concentrations at a non-equilibrium state; comparing Q to Keq indicates the reaction's direction towards equilibrium. Keq's value helps predict whether reactants or products are favored at equilibrium.
Step-by-step explanation:
Equilibrium Constants: Keq and Ktrial (Q)
The equilibrium constant (Keq) and the reaction quotient (Q) are essential concepts in Chemistry that relate to chemical reactions at equilibrium. In essence, the Keq includes the concentrations of gaseous and aqueous species at equilibrium. It is calculated by dividing the products' concentrations by the reactants' concentrations, each raised to the power of their coefficients in the balanced equation. However, solids and liquids are omitted from the Keq expression because their concentrations remain constant during a reaction.
On the other hand, Q, which is similar in formula to Keq, applies to systems not at equilibrium. It can take any value from 0 to infinity and is used to compare with Keq to determine the direction in which a reaction will proceed to reach equilibrium. If Q = Keq, the system is at equilibrium; if Q > Keq, the reaction will shift towards the reactants; and if Q < Keq, the reaction will proceed towards forming more products.
Keq's numerical value gives insight into the position of equilibrium. A very large Keq suggests that products are favored, while a very small Keq indicates that reactants are favored. When Keq has a value close to 1, there is a comparable amount of reactants and products at equilibrium. Ksp is also a type of Keq that provides similar information for solubility equilibria.