pH

pH (potential of hydrogen) is a scale of acidity from 0 to 14. It tells how acidic or alkaline a substance is. More acidic solutions, have lower pH. More alkaline solutions, have higher pH. Substances that aren't acidic or alkaline (neutral) usually have a pH of 7. Acids have a pH that is less than 7. Alkalis have a pH that is greater than 7.

There are a lot of ways for finding the pH of something. One way is to use litmus paper. The pH paper can tell you how strong the chemical is, whether it is a stronger acid or a stronger base.

pH is a measure of the concentration of protons (H+) in a solution. S.P.L. Sørensen introduced this concept in the year 1909. The p stands for the German potenz, meaning power or concentration, and the H for the hydrogen ion (H+).

The formula for calculating pH is:

${\displaystyle {\mbox{pH}}=-\log _{10}\left[{\mbox{H}}^{+}\right]}$

[H+] indicates the concentration of H+ ions (also written [H3O+], the equal concentration of hydronium ions), measured in moles per litre (also known as molarity).

Most substances have a pH in the range of 0 to 14, although extremely acidic or alkaline substances may have pH < 0, or pH > 14.

Alkaline substances have, instead of hydrogen ions, a concentration of hydroxide ions (OH-).

Some common pH values

pH values of some common substances
 pH Battery acid 1.0 Gastric acid 2.0 Lemon juice 2.4 Cola 2.5 Oxygenated water 2.5 - 3.0 Vinegar 3.0 Orange or apple juice 3.5 Beer 4.5 Coffee 5.0 Milk 6.6 Pure water 7.0 Blood 7.35 - 7.45 Plain shampoo 8.0 Sea water 8.0 Permanent wave 8.5 - 9.2 Hand soap 9.0 - 10.0 Hair dye 9.5 - 10.5 Magic straight 11.5 Household ammonia 11.5 Bleach 12.3 Caustic soda 12.7 Household lye 13.5

Neutralisation

Neutralisation can be summed up by the formula:

H+ + OH- = H2O

(acid + base = water)