water and wastewater analysis: pH, Acidity, Alkalinity and Hardness
PH. What is pH? pH is a measure of the acidity, [H + ], or basicity (alkalinity), [OH - ], of a...
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Transcript of PH. What is pH? pH is a measure of the acidity, [H + ], or basicity (alkalinity), [OH - ], of a...
pH
What is pH?
• pH is a measure of the acidity, [H+], or basicity (alkalinity), [OH-], of a solution.
• The scale is typically measured from 0 to 14.
• A pH value of 7 is considered to be neutral, neither acid nor base.
pH Scale
0 7 14
Basic[OH-]>[H+]
Acidic[H+]>[OH-] Neutral
[H+]=[OH-]
What is pH?
• pH is a logarithmic function. That is,
pH = -log10 [H+].
• This simply means that a change of one pH unit represents a 10 fold change in the acidity, e.g. pH 5 is ten times more acidic than pH 6.
For the More Advanced StudentspH = -log10 [H+]
So if:pH = 5
Then5 = -log10 [H+]
-5 = log10 [H+]
10-5 = [H+] or [H+] = 10-5 M
Measuring pH
• pH paper • Digital meters
pH levels in our lives
Water on the Webhttp://wow.nrri.umn.edu/wow/
What affects pH?
• pH can affect and be affected by atmospheric chemistry.– Dissolved CO2
– Other nonmetallic oxides• pH can affect and be affected by geological
chemistry.– Dissolved minerals– Other sources of minerals
• Buffering capacity– Determines the vulnerability of a system to pH
changes
Activity:Acids, Bases and Buffers
• See handout
• Use of Probes
• SO What??
This is what…
• Acid Precipitation• Mine tailings
• Soils have different buffering capacities• Can exceed tolerance levels for plants and
animals• Can corrode buildings and other
infrastructure
http://www.cleartheair.org/acidrain/
Acid Precipitation
http://pubs.usgs.gov/gip/acidrain/2.html
Acid Mine DrainageSeepage from an historical mine tailing deposition area. Whitewood Valley, South Dakota. USFWS photo by Joy
Gober and Scott Larson.
http://www.r6.fws.gov/contaminants/contaminants2.html
Why is pH important?
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
BacteriaPlants
Carp, Suckers, CatfishBass, Bluegill, CrappieSnails, Clams, MusselsMost Aquatic Animals
pH
Some organisms can tolerate a wider pH range.
State Water Resources Control Board-Citizen Monitoringhttp://www.swrcb.ca.gov/nps/docs/Ph.doc
German forest damaged by acid precipitation
Germania - Effetti delle precipitazioni acide sulla foresta di Erzgebirge (CREDIT: © WWF-Canon / Mauri Rautkari)
http://www.wwf.it/summit/photogallery.asp?P=4
More damage…