# 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.

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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 Students pH = -log10 [H+] So if: pH = 5 Then 5 = -log 10 [H + ] -5 = log 10 [H + ] 10-5 = [H + ] or [H + ] = 10-5 M

Measuring pH pH paperDigital meters

pH levels in our lives Water on the Web http://wow.nrri.umn.edu/wow/

What affects pH? pH can affect and be affected by atmospheric chemistry. –Dissolved CO 2 –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 Drainage Seepage 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? Some organisms can tolerate a wider pH range. State Water Resources Control Board-Citizen Monitoring http://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…

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