Soil pH - University of Minnesota土壤pH值-明尼苏达大学.ppt

Soil pH - University of Minnesota：土壤pH值-明尼苏达大学
Acid Base Chemistry
Acid-base chemistry is an important part of everyday life. The excess hydronium (H3O+) ions in acids give them interesting properties.
Acids can react with metals and other materials. The strong acid HCl is produced in your stomach to help digest food. In dilute concentrations, acids are responsible for the sour taste of lemons, limes, vinegar and other substances.
Bases are also very reactive. The strong base NaOH is used in many household cleaning agents such as oven cleaner and drain clog-remover.
H3O+ depends on the
Strength of acid and
Initial concentration
Of acid
Measuring Acidity
The acidity (or basicity) of a solution is measured using the pH scale. (this scale is used because of the very small concentrations that are being measured)
The pH scale corresponds to the concentration of hydrogen ions in a solution.
If you take the exponent of the H+ concentration and remove the negative sign, you have the pH of a solution.
For example, in pure water the concentration of hydrogen ions is 1 x 10-7 M.
Thus, the pH of a solution of pure water is 7.
The pH scale ranges from 0 to 14, where 7 is considered neutral ([H3O+ ] = [OH-]),
pH
Acid solutions are when pH is < 7.0
Alkaline solutions are when pH > 7.0
An acid can be defined as a proton donor, a chemical that increases the concentration of hydronium ions in solution.
Conversely, a base is a proton acceptor, a chemical that reduces the concentration of hydronium ions in solution (and increases the concentration of hydroxide ions).
Neutral Solution
Slightly Acidic Solution
Hydronium ions
Hydroxide ions
Water
Soil pH- Measure H+ in the Soil Solution
* pH - the negative log of the hydrogen ion(H+) concentration in the soil water solution.
pH = - log [ H+]
* the pH scale is how we measure acidity and alkalinity of solutions -----at neutral (pH =7) the number of H+ = OH-
Remember –
at pH of 6 there are 10x