How does changing concentration affect equilibrium?

Changing the concentration of reactants or products can shift the position of equilibrium, according to Le Chatelier's Principle.

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change. In the context of concentration, if the concentration of a reactant is increased, the equilibrium will shift to the right to consume the excess reactant, producing more products. Conversely, if the concentration of a product is increased, the equilibrium will shift to the left to consume the excess product, producing more reactants.

For example, consider the reversible reaction: N2(g) + 3H2(g) ⇌ 2NH3(g). If we increase the concentration of nitrogen (N2), the system will respond by shifting the equilibrium to the right to reduce the concentration of nitrogen. This will result in the production of more ammonia (NH3). On the other hand, if we increase the concentration of ammonia, the system will shift the equilibrium to the left to reduce the concentration of ammonia, resulting in the production of more nitrogen and hydrogen.

However, it's important to note that the equilibrium constant (Kc) for a reaction at a particular temperature does not change when you alter the concentration of reactants or products. The equilibrium constant is a measure of the position of equilibrium and only changes with temperature. So, while the position of equilibrium can shift to the left or right in response to changes in concentration, the value of the equilibrium constant remains the same unless the temperature changes.

In summary, changing the concentration of reactants or products in a reversible reaction can cause the position of equilibrium to shift in order to counteract the change, but it does not alter the equilibrium constant at a given temperature. This is a key concept in understanding how chemical systems respond to changes in conditions.