Question

PCl₅(g) dissociates into PCl₃(g) and Cl₂(g) when heated at 250°C and 1 atm. If the density of the gas mixture at equilibrium is 4.4 g/L, the fraction of PCl₅(g) dissociated is?

Answer 1

n=0.023 moles present in the equilibrium

4.4*208g/mol=0.021Moles of PCL5 at the start

Hence, 1mole net increases for every mole that dissociates

0.0233-0.0211=0.022 moles that dissociated.

The Fraction is 0.104, at two figures, that fraction of the original PCL5 is 1/10

$PV=nRT$ $(1atm)(1litre)=n(0.08206L-atm/mol-K)(523K)$