Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the equation: pcl5(g)→pcl3(g)+cl2(g) at 250° 0.125 m pcl5 is added to the flask. if kc = 1.80, what are the equilibrium concentrations of each gas?

Explanation:

The balanced equation is

PCl₅(g) ⇌ PCl₃(g) + Cl₂(g)

You don't give the volume of the flask, so I assume it is 1 L.

We can set up an ICE table to organize our calculations.

Check for negligibility

x is not negligible, so we must solve a quadratic.

Solve for x.

x = 0.1173

[PCl₅] = 0.125 - x = 0.125 – 0.1173 = 0.0077 mol·L⁻¹

[PCl₃] = x = 0.117 mol·L⁻¹

 [Cl₂] = x = 0.117 mol·L⁻¹

Check:

Close enough. It checks.

it is b that is the answer.