Explain what is the definition of pH with the help of examples and the equation that is used for calculating it.

pH is a measure of the acidity or alkalinity of a solution. It quantifies the concentration of hydrogen ions (H⁺) in the solution. The pH scale ranges from 0 to 14, with 7 being considered neutral. Solutions with a pH below 7 are acidic, and those with a pH above 7 are alkaline (or basic). The pH scale is logarithmic, which means that each whole pH unit represents a tenfold difference in the concentration of hydrogen ions.

The equation used to calculate pH is:

pH = -log[H⁺]

In this equation, [H⁺] represents the concentration of hydrogen ions in moles per liter (M). By taking the negative logarithm (base 10) of this concentration, we obtain the pH value.

Here are some examples to help you understand pH:

Neutral Solution: Pure water has a pH of 7 because it contains an equal concentration of hydrogen ions (H⁺) and hydroxide ions (OH⁻) at a concentration of 1 x 10⁻⁷ M. Thus, pH = -log(1 x 10⁻⁷) = 7.

Acidic Solution: Lemon juice is acidic and has a pH of around 2. This means it has a high concentration of hydrogen ions (H⁺), approximately 1 x 10⁻² M.

Basic Solution: Household ammonia is a basic solution with a pH of around 11. It has a low concentration of hydrogen ions and a higher concentration of hydroxide ions (OH⁻).

Strong Acid: Hydrochloric acid (HCl) is a strong acid with a pH close to 0, indicating a very high concentration of hydrogen ions.

Strong Base: Sodium hydroxide (NaOH) is a strong base with a pH close to 14, indicating a very low concentration of hydrogen ions.

The pH scale is essential in various scientific and practical applications, including chemistry, biology, environmental science, and industry. It helps to assess the acidity or alkalinity of substances, which can have significant effects on chemical reactions, biological processes, and the quality of various products and environments.