How do concentration changes affect the position of equilibrium?

Changes in concentration can shift the position of equilibrium either to the right or left, 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 changes, if the concentration of a reactant is increased, the system will respond by shifting the equilibrium to the right to consume the added reactant and produce more products. Conversely, if the concentration of a product is increased, the equilibrium will shift to the left to consume the added product and produce more reactants.

For example, consider the equilibrium reaction: N2(g) + 3H2(g) ⇌ 2NH3(g). If we increase the concentration of N2, the system will respond by shifting the equilibrium to the right to consume the added N2 and produce more NH3. This shift to the right decreases the concentration of N2 and H2 and increases the concentration of NH3 until a new equilibrium is established.

Similarly, if we increase the concentration of NH3, the system will respond by shifting the equilibrium to the left to consume the added NH3 and produce more N2 and H2. This shift to the left decreases the concentration of NH3 and increases the concentration of N2 and H2 until a new equilibrium is established.

It's important to note that these shifts in equilibrium position do not change the equilibrium constant, Kc, for the reaction at a given temperature. The equilibrium constant is a measure of the ratio of product concentrations to reactant concentrations at equilibrium, and it remains constant unless the temperature changes. So, while the concentrations of the reactants and products may change as the position of equilibrium shifts, the ratio of these concentrations at equilibrium remains the same.

In conclusion, changes in concentration can cause the position of equilibrium to shift in order to maintain the equilibrium constant. This is a fundamental concept in chemical equilibrium and is crucial for understanding how systems respond to changes in conditions.