Answer
$K$ = equilibrium constant
$K_p$ = equilibrium constant for gas phase reactions
$Q$ = reaction quotient
Work Step by Step
$K$ = equilibrium constant
$K$ is calculated using equilibrium concentrations and the formula $K = \frac{[C]^l[D]^m}{[A]^j[B]^j}$ for jA + kB ⇄ lC + mD
$K_p$ = equilibrium constant for gas phase reactions
$K_p$ is calculated the same as $K$, but it is specifically for gas phase reactions
$K_p = \frac{[C]^l[D]^m}{[A]^j[B]^j}$ for jA (g) + kB (g) ⇄ lC (g) + mD (g)
$Q$ = reaction quotient
Calculated like $K$ and $K_p$, but using initial concentrations instead of equilibrium concentrations.