7.19. A sample of pure PCl5 was introduced into an evacuated vessel at 473 K. After equilibrium was reached, the concentration of PCl5 was found to be 0.5 x 10-1 mol L-1. If Kc is 8.3 x 10-3 what are the concentrations of PCl3 and Cl2 at equilibrium?

Let the initial molar concentration of PCl5 per litre = x mol Molar concentration of PCl5 at equilibrium = 0.05 mol Therefore, moles of PCl5 decomposed = (x – 0.05) mol Moles of PCl3 formed = (x – 0.05) mol Moles of Cl2 formed = (x – 0.05) mol The molar conc./litre of reactants and products before the reaction and at the equilibrium point are: PCl5 PCl3 Cl2 Initial moles/litre x 0 0 At equilibrium 0.05 x – 0.05 x – 0.05 Kc = [PCl3] [Cl2] / [PCl5] => 8.3 x 10-3 = (x – 0.05)2 / 0.05 => (x – 0.05) = (4.15 x 10-4)1/2 = 2.037 x 10-2 = 0.02 moles => x = 0.05 + 0.02 = 0.07 mol Therefore, at equilibrium: Moles of PCl3 formed = (x – 0.05) mol = 0.07 – 0.05 = 0.02 mol Moles of Cl2 formed = (x – 0.05) mol = 0.07 – 0.05 = 0.02 mol

7.19. A sample of pure PCl₅was introduced into an evacuated vessel at 473 K. After equilibrium was reached, the concentration of PCl₅was found to be 0.5 x 10^-1 mol L^-1. If K_c is 8.3 x 10^-3 what are the concentrations of PCl₃and Cl₂ at equilibrium?

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Vishal Baghel | Contributor-Level 10

9 months ago

Let the initial molar concentration of PCl₅ per litre = x mol
Molar concentration of PCl₅ at equilibrium = 0.05 mol
Therefore, moles of PCl₅ decomposed = (x – 0.05) mol
Moles of PCl₃ formed = (x – 0.05) mol
Moles of Cl₂ formed = (x – 0.05) mol
The molar conc./litre of reactants and products before the re