- #1
ymhiq
- 11
- 0
Is the statement Ke=k+/k- valid for all equilibrium constants like Ka, Kx, Kp, Kc? All of the expressions I have found for this statement relate Kc, k+ and k- only.
ymhiq said:Is the statement Ke=k+/k- valid for all equilibrium constants like Ka, Kx, Kp, Kc? All of the expressions I have found for this statement relate Kc, k+ and k- only.
Chestermiller said:At equilibrium, the rate of the forward reaction must equal the rate of the reverse reaction. If the rates are expressed in terms of activities, then the equilibrium constant will be equal to the ratio of the forward- to the reverse rate constant.
So that we are on the same page, please refresh my memory of the definitions of Ka, Kc, Kx, and Kp. Do all of these refer to equilibrium constants for chemical reactions using different concentration parameters (and units)?ymhiq said:Thanks for your reply, I knew that but my doubt is exactly if Ke=Ka=Kc=Kx=Kp=(k+/k-) but in advance I Know that Ka≠Kc≠Kx≠Kp so the statement Ke=k+/k- is valid only valid for Kc according to my findings in literature. What about the others equilibrium constants? Is this statement valid for them If so what would be the differences in order to maintain the fact that Ka≠Kc≠Kx≠Kp?
Chestermiller said:So that we are on the same page, please refresh my memory of the definitions of Ka, Kc, Kx, and Kp. Do all of these refer to equilibrium constants for chemical reactions using different concentration parameters (and units)?
Chestermiller said:Yes, they are all related to one another. Start out by writing KE in terms of activities or fugacities. Then express the activities in terms of concentration times activity coefficient, or fugacities in terms of pressure times fugacity coefficient. This will let you see how the different K's are related, and where the k+ and k- can come in.
An equilibrium constant is a numerical value that represents the ratio of products to reactants at equilibrium in a reversible reaction. It is denoted by the symbol K and can be calculated using the concentrations of reactants and products at equilibrium.
Ka is the equilibrium constant for acids, Kc is the equilibrium constant for molar concentrations, Kx is the equilibrium constant for activities, and Kp is the equilibrium constant for partial pressures. They all represent the same concept of equilibrium, but use different units depending on the type of reaction.
The equilibrium constant does not directly relate to the reaction rate. However, the forward and reverse rate constants (k1 and k-1) are used to calculate the equilibrium constant. The larger the equilibrium constant, the further the reaction proceeds towards completion, and the smaller the equilibrium constant, the closer the reaction is to equilibrium.
The equilibrium constant is a constant value at a given temperature. It can change if the temperature changes, but it remains constant during a reaction at a specific temperature.
Equilibrium constants and rate constants can be calculated using the equilibrium concentrations or pressures of reactants and products, as well as the temperature. It is important to note that equilibrium constants are dimensionless, while rate constants have units of time^-1. Various mathematical methods, such as the equilibrium constant expression and the rate law, can be used to calculate these values.