What is the pH scale?

The pH scale is a numerical scale used to measure the acidity or basicity (alkalinity) of a solution. It ranges from 0 to 14, with 7 being neutral, values below 7 indicating acidity, and values above 7 indicating alkalinity.

Key Points of the pH Scale

• Definition:
  • pH stands for “potential of hydrogen” and is a measure of the hydrogen ion concentration ($\left[H^{+}\right][H^+]$) in a solution.
  • The pH scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration.
• Scale Range:
  • pH 0 to 6: Acidic solutions have more hydrogen ions ($\left[H^{+}\right][H^+]$) than hydroxide ions ($\left[O{H}^{-}\right][OH^-]$).
    • Example: Lemon juice (pH ~2), Vinegar (pH ~3).
  • pH 7: Neutral solution, where the concentration of hydrogen ions equals that of hydroxide ions.
    • Example: Pure water.
  • pH 8 to 14: Basic (alkaline) solutions have more hydroxide ions than hydrogen ions.
    • Example: Baking soda (pH ~9), Bleach (pH ~12).
• Importance:
  • pH is crucial in various fields like chemistry, biology, medicine, and agriculture.
  • In the human body, the pH of blood is tightly regulated around 7.4. Deviations can indicate health issues.
  • Soil pH affects plant growth, as different plants require different pH levels.
• Measuring pH:
  • pH can be measured using pH indicators (like litmus paper), pH meters, or universal indicator solutions.

The pH scale helps to understand the chemical nature of substances and their interactions in various environments and biological systems.