Calculate Ph for Each of The Following Situations

Introduction to pH Calculation

The pH scale measures how acidic or basic a solution is. It ranges from 0 to 14, where:

• pH 0-6: Acidic solutions (e.g., lemon juice, vinegar)
• pH 7: Neutral (e.g., pure water)
• pH 8-14: Basic solutions (e.g., baking soda, soap)

The pH scale is logarithmic, meaning each whole number change represents a tenfold difference in hydrogen ion concentration.

Basic pH Formula

The fundamental equation for pH is:

Where [H⁺] is the molar concentration of hydrogen ions in moles per liter (mol/L).

Common Situations

1. Strong Acid Solutions

For strong acids like hydrochloric acid (HCl), the pH can be directly calculated from the concentration:

2. Weak Acid Solutions

For weak acids, use the Henderson-Hasselbalch equation:

Where pKa is the acid dissociation constant, [A⁻] is the conjugate base concentration, and [HA] is the weak acid concentration.

3. Buffer Solutions

Buffers resist pH changes and can be calculated using:

Buffers are particularly useful in biological systems and laboratory settings.

Worked Examples

Example 1: Strong Acid Solution

Calculate the pH of a 0.1 M hydrochloric acid solution.

Example 2: Weak Acid Solution

Calculate the pH of a 0.01 M acetic acid solution (pKa = 4.76).

Example 3: Buffer Solution

Calculate the pH of a buffer containing 0.1 M acetic acid and 0.1 M sodium acetate (pKa = 4.76).