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When exposed to stress, a system will shift to relieve that stress and re-establish equilibrium.

In other words, the principle describes how an equilibrium position shifts. Le Chatelier’s principle describes how much a reaction favors the products or reactants under different environmental conditions. If Q is greater than K eq, then the reaction has gone past equilibrium and will proceed in the reverse direction (towards the reactants).

However, if Q is less than K eq, it has not yet achieved equilibrium, and the reaction will proceed forward (towards the products). Thus, if Q is equal to K eq, then the reaction is at equilibrium. While K eq utilizes the concentrations of species at equilibrium, Q tells us the reaction’s current position. The definition of Q is virtually identical to that of K eq: Thus, the resulting K a value is higher.Īnother important variable is the reaction quotient, Q. Since stronger acids dissociate more readily, the dissociation reaction of a strong acid favors the products. Let’s take a look at the Ka expression for the dissociation of acid, represented as HA ⇋ H + + A -: A high K a value indicates that the acid is strong. For instance, you may recall learning about the acid dissociation constant, K a. This includes the acid dissociation constant, K a the base dissociation constant, K b and even the Michaelis constant, K m. In chemistry, the capital letter “K” almost always denotes an equilibrium constant. Therefore, K eq can change if the temperature is changed.

A reaction’s equilibrium position may be changed depending on environmental conditions, such as the temperature of the environment and the presence of any catalysts. Lowercase letters (a, b, c, d) are stoichiometric coefficients. Note that in the above expression, the square brackets () denote the concentration of a certain chemical species. Given the reaction aA + bB ⇋ cC + dD, then: The equilibrium constant, known as K eq, is an expression that defines where this point is. The ratio of reactants and products at which the reaction has achieved equilibrium is expressed by the law of mass action.