Final answer:
The reaction quotient (Q) is used to determine the status of a reversible reaction at any point before it reaches equilibrium. It can predict whether the reaction will proceed forward or in reverse to achieve equilibrium based on the current concentrations or pressures of the reactants and products.
Step-by-step explanation:
The Reaction Quotient
The reaction in question, characterized by the reaction quotient (Q), is a mathematical function that describes the relative amounts of reactants and products in a reaction mixture at any given moment, before equilibrium is reached. This is not to be confused with the equilibrium constant (K), although both expressions have a similar form. The reaction quotient (Q) may be expressed in terms of concentrations (Qc) or pressures (Qp) and is especially useful for predicting the direction a reversible reaction will proceed before reaching equilibrium.
For a general balanced chemical equation aA + bB ⇌ cC + dD, the expression for Q would be the product of the concentrations of the products raised to the power of their stoichiometric coefficients, divided by the product of the concentrations of the reactants raised to the power of their stoichiometric coefficients. This can be mathematically represented as Q = ([C]c[D]d)/([A]a[B]b). At equilibrium, Q equals the equilibrium constant (K), but when not at equilibrium, the value of Q can indicate whether the reaction will proceed in the forward or reverse direction to reach equilibrium.