• pH stands for the potential of hydrogen.
• It represents the negative decimal logarithm of the concentration of hydrogen ions [H⁺] in a solution - pH = − log [H⁺].

• Acidic Solutions (<7): High concentration of H⁺ ions and appear red when using a universal indicator.
• Neutral Solutions (=7): Equal concentration of H⁺ and OH⁻ ions and appear green.
• Basic Solutions (>7): Low concentration of H⁺ ions and appear purple.

🍏 Real-World Example

• Lemon juice is acidic and has a low pH.
• Baking soda solution is basic and has a high pH.
• Pure water is neutral with a pH of 7.

• Given [H+], Find pH: pH = − log [H⁺] Example: For a 0.100 mol dm⁻³⁰.100mol dm⁻³ solution of hydrogen chloride, pH = −log 0.100 = 1.00.
• Given pH, Find [H+]: [H⁺] =10^−pH Example Hydrochloric acid with pH = 3 has a [H⁺] concentration of 10−3 = 0.001mol dm⁻³.

• pH Probe: Highly accurate and precise. Needs calibration.
• pH Paper: Gradually changes color across the whole pH range, easy to use but less accurate.

• Perform serial dilutions on Hydrochloric acid (HCl) and Sodium hydroxide (NaOH) solutions.
• Measure the pH of the resulting solutions using both pH probe and pH paper.
• Compare the results obtained from both methods and discuss reliability.