NCERT Class XI Chemistry Equilibrium Solutions

Question : 19

Total: 73

A sample of pure PCl5 was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of PCl5 was found to be 0.5 × 10–1‌mol‌L–1. If value of Kc is 8.3 × 10–3, what are the concentrations of PCl3 and Cl2 at equilibrium?
PCl5(g) ⇌ PCl3(g)+Cl2(g)

Solution:

PCl5(g) ⇌ PCl3(g)+Cl2(g)

Initial‌conc.	y	0	0
Conc.at‌equilibrium	y−x	x	x

But y - x = 0.5 × 10−1‌mol‌L−1
∴ Kc =

[PCl2][Cl2]

[PCl5]

x.x

(y−x)

orK_c$$ =

0.5×10−1

= 8.3 × 10−3
⇒ x = 2.04 × 10–2‌mol‌L–1
[PCl3] = [Cl2] = 2.04 × 10–2‌mol‌L–1

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