Question

Write a short note on $pH$.

Answer 1

The acidity or basicity of a solution depends upon its pH value. Higher the value, the more basic the solution, and the lower the pH value, the more acidic the solution is. If the pH value is seven, then the solution is considered neutral.

Complete answer:
pH denoting the potential of ${\text{hydrogen}}$ is a scale used to specify the acidity or basicity of an aqueous solution. Acidic solutions, which contain higher concentration of ${H^ + }$ are measured to have lower $pH$ values than basic or alkaline solutions. A strong acid or base completely ionises in the solution.
The pH scale is logarithmic and inversely indicates the concentration of ${\text{hydrogen}}$ ions in the solution. This is because the formula used to calculate pH approximates the negative of the base $10$ logarithm of the activity of the molar concentration of ${\text{hydrogen}}$ ions in the solution. In other words pH is the negative of the base $10$ logarithm of the activity of the ${H^ + }$ ion. It is represented by $- {\log _{10}}c$ where c is the ${\text{hydrogen}}$ concentration in moles per litre.
$pH$ scale ranges from zero to fourteen, with seven being neutral. $pH$ of less than seven indicates acidity, whereas a pH of greater than seven indicates alkaline or basic.
$pH$ is important in our day to day life. For example, $pH$ changes in the stomach due to the presence of $hydrochloric{\text{ }}acid$ activates pepsin enzymes during digestion. During farming, soil with a pH range between $6.3 - 7.3$ is good for crop growth. In a human body, blood $pH$ is somewhat neutral, if this pH changes it interrupts the proper functioning of the body.

Note:
Litmus paper is used to test whether a substance is acid or base, but it doesn’t say anything about the strength of the acidity or basicity, whereas pH shows the comparative strength of the acid and basic solutions.