Answer
The reaction quotient (Q) is also the ration of the concentration of products to reactants. but not at equilibrium.
Work Step by Step
It is useful in figuring out which direction a reaction is likely to proceed, given either the pressures or the concentrations of the reactants and the products. The Q value can be compared to the Equilibrium Constant, K, to determine the direction of the reaction that is taking place.
if Q>K reaction proceeds towards the reactants.
if Q