Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the reaction: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g)
At 250°C,0.250 M PCl₅ is added to a flask.If K_c = 1.80,what are the equilibrium concentrations of each gas?

Question

Quizplus · Accepted Answer

First, we need to set up the equilibrium expression and the ICE table:

Equilibrium expression:

Kc = [PCl5] / ([PCl3] * [Cl2])

ICE table:

PCL5  <----> PCL3    +   Cl2
I           0.250                   0                         0
C          0.250 – x                 x                         x
E         0.250 – x                 x                         x

We can substitute the equilibrium concentrations into the equilibrium expression and solve for x:

1.80 = (x)(x) / (0.250 – x)

Then, we can solve for x using the quadratic formula:

x = 0.222 M

Therefore, the equilibrium concentrations are:

[PCl5] = 0.250 – x = 0.0280 M 
[PCl3] = x = 0.222 M 
[Cl2] = x = 0.222 M

The only answer choice that matches this is A.

Phosphorus Pentachloride Decomposes to Phosphorus Trichloride at High Temperatures According