Relationship between Kp and Kc
The conversion linking the pressure and concentration forms of the equilibrium constant for a gaseous reaction.
Formula / equation
Kp = Kc(RT)^Δn
Unit
Dimensionless
In depth
Here Δn is the change in the number of moles of gas, products minus reactants. When Δn is zero the two constants are numerically equal, which is why reactions with balanced gas counts are insensitive to pressure change in this respect.
Examples in the real world
For H₂ + I₂ ⇌ 2HI, Δn = 0 so Kp = Kc; for N₂ + 3H₂ ⇌ 2NH₃, Δn = −2.