The dissociation of HI is independent of pressure while dissociation of PCl5 depends upon the pressure applied. Why?•
For 2HI ⇌ H2 + I2 Kc = x24(1−x)2 where x = degree of dissociation For PCl5 ⇌ PCl3 + Cl2 K = x2V(1−x)2; V = Volume of container. Kc for HI does not have a volume factor- and dissociation is independent of volume and hence pressure. Kc for PCl5 has volume in the denominator and hence dissociation of PCl5 depends upon the volume and consequently pressure.
