The equilibrium constant (K) is a fundamental concept in chemical equilibrium that relates the concentrations (or partial pressures) of reactants and products at a given temperature. The value of K remains constant at a particular temperature, regardless of the initial concentrations of reactants and products.
The equilibrium constant is derived from the law of mass action, which states that the rate of a chemical reaction is proportional to the product of the concentrations of the reactants. In a reversible reaction, where reactants can form products and products can also revert back to reactants, the reaction rates of the forward and reverse reactions become equal at equilibrium.
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Temperature: The equilibrium constant is affected by changes in temperature. According to the principle of Le Chatelier, when the temperature is increased, the equilibrium will shift in the direction that absorbs heat (endothermic reaction) in order to counteract the temperature change. Similarly, when the temperature is decreased, the equilibrium will shift in the direction that releases heat (exothermic reaction). As a result, the relative concentrations of reactants and products change, leading to a change in the equilibrium constant.
Concentration of reactants: The equilibrium constant is not affected by changes in the concentration of reactants once the system has reached equilibrium. At equilibrium, the forward and reverse reactions occur at equal rates, meaning the concentrations of reactants and products remain constant over time. If you were to change the concentration of a reactant, the system would respond by shifting the equilibrium in a way that compensates for the change, maintaining the same equilibrium constant. The equilibrium position would adjust to restore the original ratio of reactant and product concentrations, ensuring K remains constant.
It is important to note that although changes in the concentration of reactants do not alter the equilibrium constant, they do affect the position of the equilibrium. By altering the initial concentrations, you can manipulate the system to favor the formation of more products or reactants, but the overall ratio of concentrations will still correspond to the same equilibrium constant at that temperature.
In summary, the equilibrium constant is influenced by temperature changes, as indicated by Le Chatelier's principle, but it remains unaffected by changes in the concentration of reactants once equilibrium is reached.