# Calculating pH of a Solution

## Understanding pH Calculation

**pH** is the measure of acidity of a solution based on the concentration of **Hâº** ions present. The pH scale ranges from 0 to 14, where values below 7 are considered acidic, 7 is neutral, and values above 7 are alkaline. pH is calculated using the formula: **pH = -log[Hâº]**. This means that as the concentration of **Hâº** ions increases, the pH value decreases, indicating higher acidity.

## Mathematical Calculation for pH

Given that the solution has a **[H+]** of 0.20 M, we can calculate the pH as follows:

**pH = -log[0.2]**

**pH = 1 - log 2**

**pH = 0.699**

## Understanding the Inverse Relationship

The relationship between pH and the concentration of **Hâº** ions is inverse, meaning that as pH decreases, the concentration of **Hâº** ions increases. For every unit change in pH, there is a 10-fold change in the concentration of **Hâº** ions.

Therefore, in the given solution with a [H+] of 0.20 M, the calculated pH of 0.699 indicates a moderately acidic nature of the solution.