The equilibrium-constant expression is used to describe the concentration of reactants and products for a reaction in dynamic equilibrium. For ideal gases and ideal solutions in homogeneous equilibria, where all reactants and products are in the same phase, the extent to which a particular chemical reaction proceeds to products is given by the equilibrium equation. aA+bB⇌cC+dD , K=[C]c[D]d[A]a[B]b

where K is the equilibrium constant and the right-hand side of the equation is known as the equilibrium-constant expression.

The concentration of each product raised to its coefficient is divided by the concentration of each reagent raised to its coefficient according the the balanced chemical equation. Therefore, the higher the concentration of products, the larger the value of K will be.

Required:
Identify the proper form of the equilibrium-constant expression for the equation.
N2(g)+O2(g)⇌2NO(g)