Characteristics of Equilibrium Constants

A) Represents mathematical relationship between concentration of reactants and products in chemical reaction at equilibrium

B) Every reaction has it’s own equilibrium constant because it is constant at a particular temperature

C) The size of K gives an indication of the relative proportions of reactants and products at equilibrium. A small value of K indicates that at equilibrium only small concentrations of products are present and reactants are favoured. A large value of K indicates that products are favoured and so at equilibrium the concentrations of products will be considerably greater than those of the reactants

K= Products divided by reactants.

In theory all reactions are reversible, but some reactions are described as being essentially irreversible. Reactions with a large value of K can be considered as going to completion.

Equilibrium constants are achieved by using the ratio between equilibrium concentrations of products and reactants. They are called the reaction quotient (Q). The value of Q is only equal to K when the system is at equilibrium. If Q is less than K the concentrations of products will increase. If Q is greater than K the concentration of reactants will increase.

When the equation for a reversible reaction is written in the opposite direction the equilibrium constant becomes the reciprocal of the original equilibrium constant. The value of K depends on how the equilibrium equation is balanced.

According to the law of mass action, each concentration term in the equilibrium constant expression is raised to a power equal to it’s stoichiometric coefficient. Thus if you double a chemical equation throughout the corresponding equilibrium constant will be the square of the original value. If you triple the equation the equilibrium constant will be a cube of the original value, and so on.

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