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When a reversible reaction is carried out for a period of time, it can be seen that there will be no change in the concentration of the reactants or products. This state is called a dynamic equilibrium in which the rate of forward and backward reactions becomes equal such that the overall concentration of species remains constant.

A reaction equilibrium is determined by pressure, temperature, concentration, and volume. The value of these parameters is determined by the nature of the reaction and is set so that the equilibrium favors the product formation.

The reaction quotient is the ratio of the concentration of products to that of the reactants at any point of the reaction. It is used to determine the direction favored by the system.

There is no further change in the concentration of the reactant or products once a reaction reaches equilibrium. Therefore, the reaction quotient becomes constant, and this value of the reaction quotient is called the equilibrium constant. A higher value of equilibrium constant implies a higher concentration of products at equilibrium and thereby higher yield.

The equilibrium constant for a reaction is constant for a particular temperature. If the temperature does not change, the ratio of the concentration of products to reactants at which equilibrium is attained for a reaction is constant.

The value of the equilibrium constant is independent of the initial concentration of the reactant. Therefore, the term 鈥榗onstant鈥� in the equilibrium constant suggests that the value is constant for a reaction for a particular temperature independent of initial reactant concentration.

The two variables that can be changed that do not cause a change in equilibrium constant are pressure and concentration. The pressure of a reaction can also be changed by changing its volume, which does not alter the equilibrium constant.