We are being asked to calculate the concentration of O_{2} at equilibrium:

2 CO_{2}(g) ⇌ 2 CO(g) + O_{2}(g) K_{c} = 2.0 x 10^{-7}

**When dealing with equilibrium and K _{c}:**

• **K _{c} **→ equilibrium units are in molarity

•

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

▪ **only aqueous and gaseous species** are included in the equilibrium expression

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

We're going to calculate for the final concentration of HI(g) using the following steps:

2CO_{2}(g) ⇌ 2CO(g) + O_{2}(g) K_{c} = 2.0 x 10^{-7}

If 2.0 mol of CO_{2} is placed in a 5.0 Liter container, and decomposes according to the above equation, calculate the concentration of O_{2} at equilibrium.

A. 2.0 x 10^{-3} M

B. 4.6 x 10^{-3} M

C. 9.2 x 10^{-3} M

D. 2.7 x 10^{-3} M

E. 5.8 x 10^{-3} M