We are being asked to calculate K_{p} for the given reaction:

**2 NO _{(g)} + O_{2(g)} **

When dealing with equilibrium and K_{p}:

• **K _{p}** → equilibrium units in terms of pressure

•

$\overline{){{\mathbf{K}}}_{{\mathbf{p}}}{\mathbf{=}}\frac{\mathbf{products}}{\mathbf{reactants}}}$

▪ only gaseous species are included in the equilibrium expression

▪ the coefficient of each compound in the reaction equation will be the exponent of the pressures in the equilibrium expression

**Given: **

Consider the following reaction: 2NO(g) + O _{2}(g) ⇌ 2NO_{2}(g)

A reaction mixture at 175 K initially contains 522 torr of NO and 421 torr of O_{2}. At equilibrium, the total pressure in the reaction mixture is 748 torr. Calculate K_{p} at this temperature.