Calculation of pH of 0.2M HCl

To calculate the pH of a solution, we need to understand the concept of pH and its relation to the concentration of hydrogen ions (H+) in the solution. pH is a measure of the acidity or alkalinity of a solution and is defined as the negative logarithm (base 10) of the concentration of H+ ions in moles per liter.

Step 1: Understand the properties of HCl

Hydrochloric acid (HCl) is a strong acid that dissociates completely in water to produce H+ ions and Cl- ions. Therefore, the concentration of H+ ions in a 0.2M HCl solution would be 0.2M.

Step 2: Calculate the pH

To calculate the pH, we can use the pH formula:

pH = -log[H+]

In this case, the concentration of H+ ions is 0.2M. Therefore, substituting the value in the formula:

pH = -log(0.2)

Step 3: Evaluate the logarithm

Using a scientific calculator, we can evaluate the logarithm of 0.2:

log(0.2) ≈ -0.69897

Step 4: Calculate the pH

Substituting the calculated value into the pH formula:

pH ≈ -(-0.69897) = 0.69897

Therefore, the pH of a 0.2M HCl solution is approximately 0.69897.

Summary:
- The pH of a solution is a measure of its acidity or alkalinity.
- Hydrochloric acid (HCl) is a strong acid that dissociates completely in water to produce H+ ions and Cl- ions.
- The concentration of H+ ions in a 0.2M HCl solution is 0.2M.
- Using the pH formula, pH = -log[H+], we can calculate the pH of the solution.
- Substituting the concentration of H+ ions into the formula and evaluating the logarithm, we find that the pH of a 0.2M HCl solution is approximately 0.69897.