What is the Difference Between Kc and Kp?
🆚 Go to Comparative Table 🆚The main difference between Kc and Kp is that Kc is the equilibrium constant given as a ratio between concentrations of products and reactants, while Kp is the equilibrium constant given as a ratio between the partial pressures of products and reactants. Here are some key points about Kc and Kp:
- Kc is defined by molar concentrations and can be used for gaseous or liquid reaction mixtures.
- Kp is defined by the partial pressures of the gases inside a closed system and is used only for gaseous reaction mixtures.
- Kc is given by units of concentration, while Kp is given by units of pressure.
For a general reaction: aA(g) + bB(g) ⇋ cC(g) + dD(g), the relationship between the equilibrium constants Kc and Kp is given by the formula:
$$Kp = Kc (RT)^{\Delta n}$$
where R is the gas constant, T is the temperature, and Δn is the change in the number of moles of gas molecules (Δn = c + d - a - b). When the change in the number of moles of gas molecules is zero (Δn = 0), Kp = Kc.
Comparative Table: Kc vs Kp
The difference between $Kc$ and $Kp$ lies in the units and the conditions under which they are used. Here is a summary of their differences:
| Property | $K_c$ | $K_p$ |
|---|---|---|
| Units | Molar concentrations (mol/L) | Partial pressures (bar) |
| Conditions | Used for reactions in |