`N_2O_4(g) hArr 2NO_2(g)`. In this reaction, `NO_2` is 20% of the total volume at equilibrium. Calculate (a) vapour density. (b) percentage dissociation of `N_2O_4`.

Explanation

To solve the problem, we need to calculate the vapor density and the percentage dissociation of \( N_2O_4 \) in the equilibrium reaction \( N_2O_4(g) \rightleftharpoons 2NO_2(g) \). Given that \( NO_2 \) constitutes 20% of the total volume at equilibrium, we can follow these steps:

### Step 1: Define Initial Conditions
Let the initial number of moles of \( N_2O_4 \) be 1 mole. Therefore, initially, we have:
- Moles of \( N_2O_4 = 1 \)
- Moles of \( NO_2 = 0 \)

### Step 2: Define Changes at Equilibrium
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