General Chemistry
Le Châtelier's principle explains how a system at equilibrium responds to stress and adjusts to regain equilibrium. Chemical reactions can be affected by changes in concentration, volume, pressure, and temperature. When the concentration of reactants increases or the concentration of products decreases, the reaction will shift to favor producing the products until equilibrium is reached again. Conversely, increasing the concentration of products or removing reactants will favor the reverse reaction rate.
In reactions containing a gas, increasing volume or decreasing pressure will shift the reaction toward the side with more moles, while decreasing volume or increasing pressure will shift the reaction toward the side with fewer moles. For endothermic reactions, heat acts as a reactant, so increasing temperature will shift the reaction toward the products. In exothermic reactions, heat acts as a product, so increasing temperature will favor the reverse reaction, pushing the reaction toward the reactants.
Lesson Outline
<ul> <li>Le Chatelier's Principle = a reaction regaining equilibrium state in response to stressors</li> <li>Examples of stressors in chemical reactions: <ul> <li>Changes in concentration</li> <li>Changes in volume</li> <li>Changes in pressure</li> <li>Changes in temperature</li> </ul> </li> <li>Changes in Concentration: <ul> <li>Increasing concentration of reactants = shift to the right</li> <li>Increasing concentration of products = shift to the left</li> </ul> </li> <li>Changes in Volume, Pressure (involving gases): <ul> <li>Increasing volume = shift to the side with more moles</li> <li>Decreasing volume = shift to the side with fewer moles</li> <li>Increasing pressure = shift to the side with fewer moles</li> <li>Decreasing pressure = shift to the side with more moles</li> </ul> </li> <li>Changes in Temperature: <ul> <li>Endothermic reactions = increasing temperature shifts towards the products</li> <li>Exothermic reactions = increasing temperature shifts towards the reactants</li> </ul> </li> </ul>
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FAQs
Le Châtelier's Principle states that when a reversible reaction at equilibrium experiences a change in concentration, temperature, or pressure, the system will respond in a way that counteracts the disturbance and restores equilibrium.
When the concentration of a reactant or product in a reversible reaction is changed, the system will respond by shifting the position of equilibrium to counteract the change. If the concentration of a reactant is increased, the system will shift to consume that reactant by forming more products. Conversely, if the concentration of a product is increased, the system will shift to consume that product by forming more reactants. This helps maintain equilibrium in the reaction.
According to the Ideal Gas Law, pressure and volume are inversely proportional when temperature and the amount of gas are constant. Le Châtelier's Principle predicts that increasing the pressure for a reaction involving gases causes the system to shift towards the side with fewer moles of gas, while a decrease in pressure will shift the system towards the side with more moles of gas. Similarly, an increase in volume will shift the equilibrium towards the side with more moles of gas, and a decrease in volume will shift the system towards the side with fewer moles of gas.
Temperature plays a significant role in determining the position of equilibrium for endothermic and exothermic reactions. For an endothermic reaction, increasing the temperature will shift the equilibrium to the side that absorbs heat (products), while decreasing the temperature will favor the side that releases heat (reactants). For an exothermic reaction, increasing temperature will shift the equilibrium towards the side that releases heat (reactants), while decreasing the temperature will favor the side absorbing heat (products). This means that a higher temperature favors the formation of products in endothermic reactions and reactants in exothermic reactions, while lower temperatures have the opposite effect.
