Question

Phosphorus pentachloride decomposes according to the chemical equation. A 0.135 mol sample of PCl5(g) is injected into an empty 2.15 L reaction vessel held at 250 °C. Calculate the concentrations of PCl5(g) and PCl3(g) at equilibrium.

Answer 1

Kc= Equilibrium cosntant = 0.041 at 250 deg.c

for PCl5----> PCl3+Cl2 , Kc =[Cl2] [PCl3]/ [PCl5] =0.041

                        PCl5                        PCl3                     Cl2

Initilal               0.135/2.15 =0.063                0                         0

let x= change of PCl5 due to equilibium

Equilibrium 0.063-x                                  x                               x

Kc= x²/(0.063-x)= 0.041

this equaiion can be solved using solver of excel by asssuming some initial value of x=0.0343

PCl5= 0.063-0.0343= 0.0287    PCl3= 0.0343 and Cl2= 0.0343