By definition, acids have a pH of less than 7, while bases have a pH of more than 7 and neutral water has a pH of exactly 7. The lower the pH, the stronger the acid, so usually strong acids have a pH of 0 to 2 while weak acids have a pH of 3 to 5. Solutions with pH of 6 are technically acidic, but only barely.
At the other end of the scale, strong bases have pH of about 12 to 14, while weak bases have a pH of about 9 to 11 and solutions with a pH of 8 are technically basic but only slightly. (The human bloodstream has a pH of about 7.4 normally.)
It's also possible in extreme circumstances for acids to go below 0 or bases to go above 14. These are very strong acids and bases respectively.
What pH is actually measuring is the negative log base 10 of the activity of hydrogen ions in the solution.
`pH = - log_10 (a_{H+})`
Indeed, you can actually put p on anything and that means the negative log base 10 of its activity; but mainly we just use it for hydrogen.
No comments:
Post a Comment