When the volume of a system is increased, the concentration of the reactants in the system decreases. This means there are fewer molecules of N2O4 available to react with each other, so less N2O4 will be formed. Conversely, when the volume of a system is decreased, the concentration of the reactants increases. This means more molecules of N2O4 are available to react with each other, so more N2O4 will be formed.

The relationship between the volume of a system and the amount of N2O4 formed is described by the following equation:

```

1/V = k[N2O4]

```

In this equation, V represents the volume of the system, k represents the rate constant for the reaction, and [N2O4] represents the concentration of N2O4 in the system.

This equation shows that as the volume of the system increases, the concentration of N2O4 decreases, and as the volume of the system decreases, the concentration of N2O4 increases. This is consistent with the general principle that the concentration of a gas is inversely proportional to the volume of the system.