chemistry problem

Question

Phosphorus pentachloride decomposes according to the chemical equation

PCl5(g)↽−−⇀PCl3(g)+Cl2(g)𝐾c=1.80 at 250 ∘CPCl5(g)↽−−⇀PCl3(g)+Cl2(g)�c=1.80 at 250 ∘C

A 0.3476 mol0.3476 mol sample of PCl5(g)PCl5(g) is injected into an empty 3.95 L3.95 L reaction vessel held at 250 ∘C.250 ∘C.

Calculate the concentrations of PCl5(g)PCl5(g) and PCl3(g)PCl3(g) at equilibrium.

Answer 1

Set up an ICE table

0.3476 mols PCl5 / 3.95 L = 0.088 M

PCl5(g) <==> PCl3(g) + Cl2(g)

0.088..............0..............0..........Initial

-x...................+x............+x.........Change

0.088-x...........x...............x..........Equilibrium

Kc = [PCl3][Cl2] / [PCl5]

1.80 = (x)(x) / 0.088-x

1.80 = x² / 0.088-x

x² = 0.1584 - 1.80x

x² - 0.1584 + 1.80x = 0

x = 0.084 M

At equilibrium..

[PCl5] = 0.088 - 0.084 = 0.004 M

[PCl3] = x = 0.084 M