Question

Define \(\mathrm{pH}\) and give its mathematical representation.

Short answer

Answer: pH is a measure of the acidity or alkalinity of a solution, defined as the negative logarithm (base 10) of the hydrogen ion (H⁺) concentration in terms of moles per liter (mol/L). The mathematical representation of pH is given by the formula: pH = -log₁₀[H⁺].

Step-by-step solution

Definition of pH

pH is a measure of the acidity or alkalinity of a solution. It is defined as the negative logarithm (base 10) of the hydrogen ion (H⁺) concentration in terms of moles per liter (mol/L). A pH value can range from 0 to 14, where a pH of 7 represents a neutral solution (neither acidic nor alkaline). A pH value less than 7 indicates an acidic solution, and a value greater than 7 indicates an alkaline solution.

Mathematical Representation of pH

The mathematical representation or formula for pH is given by: pH = -log₁₀[H⁺] where pH is the pH value, and [H⁺] denotes the hydrogen ion concentration in the solution measured in moles per liter (mol/L).

Key concepts

Understanding Acidity

Acidity refers to how strong or weak an acid is in a solution. It is determined by the presence of hydrogen ions (H⁺). Solutions with a higher concentration of hydrogen ions are considered more acidic. The pH scale is used to measure acidity, where values less than 7 indicate acidic solutions.

An acidic solution can affect the taste, stability, and chemical behaviors of substances. Everyday examples include lemon juice and vinegar, both of which have a low pH and are considered acidic.

Exploring Alkalinity

Alkalinity is the opposite of acidity and measures the strength of a base in a solution. It is determined by the concentration of hydroxide ions (OH⁻). Solutions with a pH greater than 7 are alkaline, also known as basic.

Alkaline substances tend to have properties like bitter taste and slippery feel. Common examples include baking soda and soap, which have higher pH levels and are used in cleaning and cooking applications. Alkalinity plays a crucial role in balancing the pH of various environments, from aquatic systems to agricultural soils.

Hydrogen Ion Concentration

The hydrogen ion concentration, denoted as [H⁺], is crucial in determining a solution's pH. It represents the number of hydrogen ions present in a given volume of solution, measured in moles per liter (mol/L).

When you calculate pH using the formula \(\text{pH} = -\log_{10}[H^+]\), you're essentially finding out how acidic or basic a solution is based on these ions.

• Higher [H⁺] means lower pH (more acidic).
• Lower [H⁺] means higher pH (more alkaline).

Understanding hydrogen ion concentration helps in various fields like chemistry, biology, and environmental science.

Neutral Solution

A neutral solution has a pH of 7. This means the concentration of hydrogen ions equals the concentration of hydroxide ions. It is neither acidic nor alkaline.

Pure water is a classic example of a neutral solution. Having a balanced pH of 7 is important in many biological and chemical processes, such as maintaining proper cell function and facilitating chemical reactions.

In real-world applications, achieving neutrality is essential in products like skincare, where the balance ensures compatibility with the human body. Neutral solutions serve as a reference point for assessing other solutions' acidity or alkalinity.