We are being asked to determine which of the given conditions must be true for the reaction:

**2 SO _{2}(g) + O_{2}(g) ⇌ 2 SO_{3}(g)**

**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

**Given: **

**Initial Concentrations:**

Since the container is only 1 L, the mole values of each will equal the initial concentration:

Given

2SO_{2}(g) + O_{2}(g) ⇌ 2SO_{3}(g)

Suppose 0.10 mol of SO_{2} and 0.10 mol of O_{2} are added to a 1-L vessel. At equilibrium, which of the following conditions must be true?

A) [O_{2}] = 2[SO_{3}]

B) [SO_{2}] = [O_{2}]

C) [SO_{2}] > [O_{2}]

D) [SO_{2}] < [O_{2}]

E) [SO_{2}] = [O_{2}] = [SO_{3}]