Question

Pcl5 dissociates according to the reaction pcl5 gives pcl3 + cl2 at 523 atm. Kp is equal to 1.78 atm. Find the density of the equilibrium mixture at the total pressure of 1 atm

Answer 1

PCl5 dissociates as:

PCl5 ---------> PCl3 + Cl2

If ρ will be degree / constant of dissociation at STP,

t=0

PCl5 = 1

PCl3 = 0

Cl2 = 0

When equilibrium:

PCl5 = 1 – p

PCl3 = p

Cl2 = p

No. of mole at eq. = 1 – p + p + p = 1 + p

Pressure of PCl5, PCl3 and Cl2 will be:

ρ (PCl3) = ρ ρ / 1 + ρ

ρ (Cl2) = ρ ρ / 1 + ρ

p (PCl5) = (1 – p) p / 1 + p

K p = p (PCl3) X p (Cl2) / p (PCl5)

K p = [(p p / 1 + p) X (p p / 1 + p)]/[ (1 – p) p / (1 + p)]

= p^2 p / (1 – p) ^ 2