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Phosphorus pentachloride decomposes according to the chemical equation PCl5(g) ?

ID: 852767 • Letter: P

Question

Phosphorus pentachloride decomposes according to the chemical equation PCl5(g) ? PCl3(g) + Cl2(g) Kc=1.80 at 250 C A 0.156 mol sample of PCl5(g) is injected into an empty 2.10 L reaction vessel held at 250 C. Calculate the concentrations of PCl5(g) and PCl3(g) at equilibrium. Phosphorus pentachloride decomposes according to the chemical equation PCl5(g) ? PCl3(g) + Cl2(g) Kc=1.80 at 250 C A 0.156 mol sample of PCl5(g) is injected into an empty 2.10 L reaction vessel held at 250 C. Calculate the concentrations of PCl5(g) and PCl3(g) at equilibrium. Kc=1.80 at 250 C A 0.156 mol sample of PCl5(g) is injected into an empty 2.10 L reaction vessel held at 250 C. Calculate the concentrations of PCl5(g) and PCl3(g) at equilibrium.

Explanation / Answer

PCl5(g) <> PCl3(g) + Cl2(g) Kc=1.80 at 250 C ;

initially:

[PCl5] = mol/V = 0.156 / 2.1 = 0.07428571 M

[PCl3] = 0 [Cl2] = 0

in equilibrium:

[PCl5] = 0.07428571 - x

[PCl3] = 0 + x

[Cl2] = 0 + x

substitute ion Kc

Kc = [PCl3][Cl2]/[PCl5]

1.8 = x*x/(0.07428571 - x)

x = 0.07144957

substitute

[PCl5] = 0.07428571 - 0.07144957 = 0.00283614 M

[PCl3] = 0 + 0.07144957 = 0.07144957 M