Nitrogen gas and chlorine gas will react to form nitrogen monochloride gas. 5 moles of nitrogen and 10 moles of chlorine are mixed in a previously evacuated 2 L flask at 500 K. After equilibrium has been established, there are 3 moles of NCl (g) present. What is the equilibrium constant (Kc) for this reaction at 500 K

0.30

Explanation:

Step 1: Calculate the known initial and equilibrium molar concentrations

[N₂]i = 5 mol/2 L = 2.5 M

[Cl₂]i = 10 mol/2 L = 5 M

[NCl]e = 3 mol/2 L = 1.5 M

Step 2: Make an ICE chart

        N₂(g) + Cl₂(g) ⇄ 2 NCl(g)

I         2.5       5                0

C        -x        -x              +2x

E      2.5-x    5-x               2x

Step 3: Find the value of x

We know that [NCl]e = 2x = 1.5 ⇒ x = 0.75 M

Step 4: Calculate the concentrations at equilibrium

[N₂]e = 2.5-x = 2.5-0.75 = 1.75 M

[Cl₂]e = 5-x = 5-0.75 = 4.25 M

[NCl]e = 1.5 M

Step 5: Calculate the equilibrium constant (Kc)

Kc = [NCl]² / [N₂] × [Cl₂]

Kc = 1.5² / 1.75 × 4.25 = 0.30