Question

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

Answer 1

Hint: In chemistry, $pH$ denotes the potential of hydrogen or power of hydrogen. It is a scale used to specify the acidity or basicity of a given aqueous solution. Note that acidic solutions have higher concentrations of ${H^ + }$ ions and they have lower $pH$ values than basic or alkaline solutions.

Complete answer:
$pH$ is defined as the measure of the concentration of hydrogen ions which is used to measure the acidity or alkalinity of a given solution. The equation that is used for the calculation of $pH$ is as follows:
$pH = - \log [{H^ + }]$
The range of the$pH$scale varies from $0$ to $14$ . The solutions which have $pH$ in the range from $0$ to $7$ on the $pH$ scale are said to be acidic solutions. The solutions which have $pH$ in the range from $7$ to $14$ on the $pH$ scale are said to be basic solutions. The solutions having the $pH$ value $7$ on the $pH$ scale are called neutral solutions. Look at the examples given in the below table:

Example	Nature of solution	$pH$ value
Lemon juice	Acid	$2$
Orange juice	Acid	$3$
Water	Neutral	$7$
Sugar solution	Neutral	$7$
Baking soda	Base	$9$
Liquid drain cleaner	Base	$13$

Note:
The $pH$ scale is logarithmic and inversely indicates the concentration of hydrogen ions in the solution. This is because the formula used to calculate $pH$ approximates the negative of the base $10$ logarithm of the molar concentration of hydrogen ions in the solution. To be precise, $pH$ is the negative of the base $10$ logarithm of the activity of the ${H^ + }$ ion.