This episode focuses on the Equilibrium Constant (K), which mathematically quantifies the position of a chemical equilibrium. K is defined by the expression: Products over Reactants, where the molar concentration of each substance, represented by brackets [ ], is raised to the power of its stoichiometric coefficient. A crucial rule is to exclude pure solids (s) and pure liquids (l) from the K expression, only including gases (g) and aqueous solutions (aq) because the concentrations of solids and pure liquids are constant. The value of K indicates which side of the reaction is favored: a large K (K>1) means the equilibrium favors products, while a small K (K<1) means it favors reactants.