Can occur in physical or chemical systems.

Characteristics

• Dynamic
• Closed system
• Same concentration because of same rates
• No change in macroscopic properties
• Equilibrium can be reached from either direction. $Reactant\leftrightharpoons Product$ Lies to the right is more products, or the forward reaction. To the left is more reactants, favouring the backward reaction. You made this mistake on a test before, so beware.

K values

$K=\frac{[C{]}^c[D{]}^d}{[A{]}^a[B{]}^b}$ Its also just:$\frac{Products}{Reactants}$