The combination of NO₂ and H₂O is not a simple molecule. Instead, it represents a reaction that produces nitrous acid (HNO₂) and nitric acid (HNO₃).

Here's the breakdown:

* NO₂ (Nitrogen Dioxide): A toxic and reddish-brown gas.

* H₂O (Water): The familiar liquid we drink.

Reaction:

When nitrogen dioxide (NO₂) reacts with water (H₂O), the following reaction occurs:

3 NO₂ + H₂O → 2 HNO₃ + NO

This reaction produces:

* Nitric Acid (HNO₃): A strong acid commonly used in fertilizer production.

* Nitrous Acid (HNO₂): A weaker acid, often present in acidic rain.

* Nitric Oxide (NO): A colorless gas that can react further in the atmosphere.

Importance:

This reaction is crucial in understanding the formation of acid rain, as it demonstrates how nitrogen oxides released from combustion processes can react with water in the atmosphere to produce acidic compounds.

Note: The exact products and their proportions can vary depending on factors like temperature and the presence of other gases.