How is Kc different from Kp?

Kc and Kp are equilibrium constants, but Kc is expressed in terms of concentrations while Kp is expressed in terms of partial pressures.

Kc and Kp are both equilibrium constants that are used in the study of chemical reactions. They are used to express the position of equilibrium for a particular reaction. However, the main difference between them lies in the way they are expressed. Kc, or the equilibrium constant in terms of concentration, is expressed in terms of the molar concentrations of the reactants and products. On the other hand, Kp, or the equilibrium constant in terms of pressure, is expressed in terms of the partial pressures of the reactants and products.

The equilibrium constant Kc is used when dealing with reactions in solution. It is calculated by taking the product of the concentrations of the products, each raised to the power of its stoichiometric coefficient, divided by the product of the concentrations of the reactants, each raised to the power of its stoichiometric coefficient. It's important to note that only gases and aqueous solutions are included in the equilibrium expression for Kc.

Kp, on the other hand, is used when dealing with reactions involving gases. It is calculated in a similar way to Kc, but instead of using concentrations, the partial pressures of the gases are used. The partial pressure of a gas is the pressure that the gas would exert if it were alone in the container. It's worth noting that the relationship between Kp and Kc is given by the equation Kp = Kc(RT)^(Δn), where R is the ideal gas constant, T is the temperature in Kelvin, and Δn is the change in the number of moles of gas.

In summary, while both Kc and Kp serve the same fundamental purpose of expressing the position of equilibrium for a reaction, they are used in different contexts and are calculated using different quantities. Kc is used for reactions in solution and is calculated using concentrations, while Kp is used for reactions involving gases and is calculated using partial pressures.