The question "What is the equilibrium constant for reaction SO2?" is incomplete. You need to specify the complete chemical reaction involving SO2 for which you want to know the equilibrium constant.

Here's why:

* SO2 can participate in many different reactions. For example, it can:

* React with oxygen to form sulfur trioxide (SO3): 2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g)

* React with water to form sulfurous acid (H2SO3): SO2 (g) + H2O (l) ⇌ H2SO3 (aq)

* Participate in the combustion of fuels, contributing to acid rain.

To help you, please provide the following information:

1. The complete chemical equation for the reaction involving SO2.

2. The temperature at which you want to know the equilibrium constant.

Once you provide these details, I can help you find the equilibrium constant (K) for the specific reaction.