The degree of dissociation is 0.4 at 400 K and 1 atm for the gaseous reaction
`PCl_5 iff PCl_5 + Cl_2`
Assuming ideal behaviour of all the gases, calculate the density of equilibrium mixture at 400 K and 1 atm.

Explanation

To calculate the density of the equilibrium mixture for the reaction \( PCl_5 \rightleftharpoons PCl_3 + Cl_2 \) at 400 K and 1 atm, we will follow these steps:

### Step 1: Define the degree of dissociation
Let the degree of dissociation \( \alpha = 0.4 \). This means that 40% of \( PCl_5 \) dissociates into \( PCl_3 \) and \( Cl_2 \).

### Step 2: Set up the initial and equilibrium moles
Assume we start with 1 mole of \( PCl_5 \):
- Initial moles of \( PCl_5 \) = 1
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