equilibrium constant
- Noun:
- A numerical value expressing the ratio of product concentrations to reactant concentrations at chemical equilibrium: The equilibrium constant is a fundamental quantity in chemistry that quantifies the position of equilibrium for a reversible reaction. It is defined when the rates of the forward and reverse reactions are equal, and the concentrations of all species remain constant.
- Noun:
- The equilibrium constant for the reaction is very large, indicating the products are highly favored.
- To predict the direction of a reaction, chemists compare the reaction quotient to the equilibrium constant.
- Calculating the equilibrium constant requires precise measurements of concentrations at equilibrium.
"Temperature dependence of the equilibrium constant": The value of the equilibrium constant for a given reaction changes with temperature, as described by the van 't Hoff equation.
- Understanding the temperature dependence of the equilibrium constant is crucial for industrial process design.
"To write an equilibrium constant expression": The process of formulating the ratio of concentrations (or partial pressures) according to the law of mass action for a specific balanced chemical equation.
- For the reaction aA + bB ⇌ cC + dD, the equilibrium constant expression is K = ([C]^c [D]^d) / ([A]^a [B]^b).
Equilibrium (n): The state in a reversible chemical reaction where the concentrations of reactants and products no longer change with time because the forward and reverse reaction rates are equal.
- The system eventually reached a dynamic equilibrium.
Reaction quotient, Q (n): A ratio of concentrations (or partial pressures) of products to reactants at any point during a reaction, not necessarily at equilibrium. It is compared to K to determine the reaction's direction.
- If Q is less than K, the forward reaction is favored to reach equilibrium.
- K (n): A common abbreviation for the equilibrium constant.
- Kc (n): Specifically denotes an equilibrium constant expressed in terms of molar concentrations.
- Kp (n): Specifically denotes an equilibrium constant expressed in terms of partial pressures for gaseous reactions.
Law of mass action: The principle that at a given temperature, the rate of a chemical reaction is proportional to the product of the concentrations (or activities) of the reactants. This law leads directly to the equilibrium constant expression.
- The equilibrium constant is derived from the law of mass action.
Le Châtelier's principle: A qualitative rule stating that if a change of condition is applied to a system in equilibrium, the system will shift to counteract that change. It predicts how changes affect the position of equilibrium but not the value of the equilibrium constant (unless temperature changes).
- According to Le Châtelier's principle, adding more reactant will shift the equilibrium to the right, but the equilibrium constant remains the same at constant temperature.
- (chemistry) the ratio of concentrations when equilibrium is reached in a reversible reaction (when the rate of the forward reaction equals the rate of the reverse reaction)