When a reaction at equilibrium is disturbed by the addition of products, (a) Which way will the reaction shift? (b) After the reaction is done shifting, will the product concentration be the same as before the disturbance, greater than before the disturbance, or less than before the disturbance? Explain your answer. (c) Repeat part (b) but for the reactant concentration.

Chemical equilibrium occurs when the rate of the forward reaction is equal to the rate of the reverse reaction in a chemical process, resulting in no net change in the concentrations of the reactants and products. This dynamic state is crucial because it's the point at which the system's energy is at a minimum, and the concentrations become constant, though not necessarily equal. In a closed system, this can be represented by a balanced chemical equation. An important characteristic of equilibrium is that it can be disrupted by external changes like temperature, pressure, or concentration, but the system will attempt to restore equilibrium, as per Le Chatelier's principle.

Think of a seesaw perfectly balanced with two children of equal weight. If one child were to suddenly have extra weight added, the seesaw would tilt — this is similar to adding a product or reactant in a chemical equation. The system will then try to compensate, much like how the children might adjust their positions on the seesaw to balance it once again.

When the chemical equilibrium in a reaction is disturbed, the system experiences what is called a 'reaction shift.' This is the process by which the reaction adjusts itself to a new equilibrium state. According to Le Chatelier's principle, the direction of this shift will be towards the side (reactants or products) that will counteract the change.

If the concentration of products is increased, the reaction will shift towards the reactants to reduce the product concentration, much like adding more riders on one end of a balanced see-saw causes it to tip, and riders must shift their positions to restore balance. This shift can be either to the left, indicating a favor towards the reactants (as in this example), or to the right, indicating a preference towards producing more products when reactants are added. These shifts are fundamental in understanding how various conditions affect the yield of products in industrial and biochemical processes.

Changes in the concentration of reactants or products can dramatically affect the position of chemical equilibrium. When the concentration of a substance on one side of a balanced equation is increased, the system will shift to the opposite side to try and reduce the effect of this change. This shift leads to a change in the concentration of all substances involved in the reaction.

For instance, if more product is added to a system at equilibrium, the reaction shifts to the left, meaning that some of the product is converted back to reactants, thereby increasing the reactant concentration and decreasing the product concentration. However, the change is not entirely reversed to the original starting conditions. The new equilibrium will be established at different concentrations but the ratio of the concentrations, known as the equilibrium constant, remains unchanged unless affected by temperature changes. This concept is crucial for predicting how chemical reactions will behave when subjected to different conditions, and it has wide-reaching applications in chemical engineering, pharmacy, and environmental science.