What is pH?

In chemistry, pH is the negative of the logarithm of the concentration of hydrogen ion / hydronium ion. It has the formula as follows:
pH=−log[H3O+]
Here, pH is also considered as potential of hydrogen ion. It is a measure of basic or acidic nature of an aqueous solution. The pH of acidic solution is in the range from 0 to 6, and that of the basic solution ranges from 8 to 14. The pH of neutral solution is 7.
[H3O+] is concentration of hydronium ion that is measured in moles per liter (i.e., molarity). Basic solutions have lower concentration of hydronium ion, whereas acidic solutions have higher concentration of hydronium ion.
The above equation can also be written as
[H3O+] = 10-pH
This equation helps in measuring hydronium ion concentration from pH.
Further Reading:
My First Book About Chemistry (Dover Children’s Science Books)*
Chemistry For Dummies (For Dummies (Lifestyle))*
Chemistry: Concepts and Problems: A Self-Teaching Guide*
* – Affiliate link