**PH Value of NO2 in Aqueous Solution**

**Introduction**
The pH value of a solution indicates its acidity or alkalinity. It is a scale that ranges from 0 to 14, where 0 represents highly acidic, 7 represents neutral, and 14 represents highly alkaline (basic) solutions. In the case of NO2 (nitrogen dioxide) in an aqueous solution, the pH value can be determined by considering its reaction with water and the resulting ions.

**Reaction of NO2 with Water**
When nitrogen dioxide (NO2) dissolves in water, it reacts with it to form nitric acid (HNO3). The reaction can be represented by the following equation:

NO2 + H2O → HNO3

**Formation of Acidic Solution**
As the reaction between NO2 and water produces nitric acid (HNO3), the resulting solution becomes acidic. Nitric acid is a strong acid and dissociates almost completely in water, releasing hydrogen ions (H+). The presence of hydrogen ions makes the solution acidic, which is reflected in the pH value.

**pH Calculation**
To determine the pH value of the solution, we need to consider the concentration of hydrogen ions (H+) in the solution. The concentration of H+ ions can be found using the equation:

pH = -log[H+]

Since nitric acid (HNO3) is a strong acid, it completely dissociates in water to release one hydrogen ion (H+) for each molecule of acid. Therefore, the concentration of hydrogen ions in the solution is equal to the concentration of nitric acid.

**Conclusion**
In conclusion, the pH value of NO2 in an aqueous solution is determined by the formation of nitric acid (HNO3) when NO2 reacts with water. As nitric acid is a strong acid, it dissociates completely, releasing hydrogen ions (H+) and making the solution acidic. The pH value can be calculated based on the concentration of hydrogen ions in the solution, which is equal to the concentration of nitric acid.