PH
From Wikipedia, a free encyclopedia written in simple English for easy reading.
pH (Power of Hydrogen) is a scale of acidity from 0 to 14. It tells how acidic or alkaline a substance is. The lower the pH, the more acidic is the solution. The higher the pH, the more alkaline is the solution. Substances which are neither acidic (neutral) usually have a pH of 7. Acids have a pH less than 7. Alkalis have a ph greater than 7.
In fact, pH is a measure of the concentration of protons (H+) in a solution. S.P.L. Sørensen introduced this concept in 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:
[H+] indicates the concentration of H+ ions (also written [H3O+], concentration of the equivalent hydronium ions), measured in moles per litre (also known as molarity).
Most substances have a pH in the range 0 to 14, although extremely acidic or basic substances may have pH < 0, or pH > 14.
Basic substances have, instead of Hydrogen ions, a concentration of Hydroxide ions (OH-).
[edit] Some common pH values
pH | |
Battery acid | 1.0 |
Stomach | 2.0 |
Lemon juice | 2.4 |
Cola | 2.5 |
Vinegar | 2.9 |
Orange or apple juice | 3.5 |
Beer | 4.5 |
Coffee | 5.0 |
Tea | 5.5 |
Acid rain | < 5.6 |
Milk | 6.5 |
Pure water | 7.0 |
Blood | 7.34 - 7.45 |
Sea water | 8.0 |
Hand soap | 9.0 - 10.0 |
Household ammonia | 11.5 |
Bleach | 12.5 |
Household lye | 13.5 |
[edit] Neutralisation
Neutralisation can be summed up by the formula:
- H+ + OH- = H2O