A sample of pure PCl5 was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of PCl_5 was found to be 0.5×10−1molL−1.IfvalueofKcis8.3×10−3, what are the concentrations of PCl3 and Cl2 at equilibrium?\\
PCl5(g)↔PCl3(g)+Cl2(g)
Let the concentrations of both PCl3 and Cl2 at equilibrium be x molL−1. The given reaction is:
PCl5(g)↔PCl3(g)+Cl2(g)AT equilibrium0.5×10−1mol L−1z mol L−1x mol L−1
It is given that the value of equilibrium constant. Kc is 8.3×1−3
Now we can write the expression for equilibrium as:
[PCl2][Cl2][PCl5]=Kc⇒x×x0.5×10−1=8.3×10−3⇒x2=4.05×10−4⇒x=2.04×10−2=0.0204=0.02 (approximately)
Therefore, at equilibrium,
[PCl3]=[CL2]=0.02 mol L−1