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3.0 moles of is introduced in a 1 L closed reaction vessel at 380 K. The number of moles of at equilibrium is (Round off to Nearest Integer)

Question

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3.0 moles of  is introduced in a 1 L closed reaction vessel at 380 K. The number of moles of  at equilibrium is  (Round off to Nearest Integer)

Canvas Classes · Accepted Answer

🧠 Solve the Quadratic —  Not Small, So the Approximation Fails

The reaction is  with . Initial  M (since  mol in  L), and .

The visible clue:  is not small. So we cannot use the  approximation — the dissociation is substantial. The first move is to set up the quadratic exactly.

🗺️ Working It Out

Let  = M of PCl₅ dissociated.

| Species |  |  |  |
|---|---|---|---|
| Equilibrium |  |  |  |

Apply the quadratic formula:

So  M. Since  L,  mol.

Express in  form: .

Nearest intege

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