pHpH
Gary BatesGary Bates
University of ArkansasUniversity of Arkansas
Review outlineReview outline
Basic chemistryBasic chemistry OrbitalsOrbitals IonsIons MoleculesMolecules Properties of waterProperties of water
OutlineOutline
What is pH?What is pH? pH scalepH scale Effects and indicatorsEffects and indicators pOHpOH AcidsAcids BasesBases BuffersBuffers ReviewReview
pHpH
Definition:*Definition:* pH=-log [HpH=-log [H++] ]
In wordsIn words The negative logarithm of the The negative logarithm of the
concentration of hydronium ionsconcentration of hydronium ions
Log infoLog info
Logarithm- Logarithm- Inverse of exponentialInverse of exponential ten fold differences between numbersten fold differences between numbers Difference inDifference in
pH of 1 & 2pH of 1 & 2 pH of 1 & 3pH of 1 & 3 pH of 6 & 3pH of 6 & 3
ConcentrationConcentration pH of 7pH of 7 10107 7 HH++
http://en.wikipedia.org/wiki/Logarithm
Definition:Acids and BasesDefinition:Acids and Bases
AcidsAcids are substances that dissociate are substances that dissociate in water and release hydrogen ions in water and release hydrogen ions (H(H++).).
Bases Bases are substances that either are substances that either take up hydrogen ions (Htake up hydrogen ions (H++) or release ) or release hydroxide ions (OHhydroxide ions (OH--).).
pH ScalepH Scale
pH scale used to indicate acidity and pH scale used to indicate acidity and basicity of a solution.basicity of a solution. Ranges from 0-14Ranges from 0-14
7 = Neutral7 = Neutral >7 = Base>7 = Base <7 = Acid<7 = Acid
Logarithmic ScaleLogarithmic Scale
www.greenair.com/images/tt3.gif
http://staff.jccc.net/PDECELL/chemistry/phscale.html
Importance Importance
pH is important in most aspects of pH is important in most aspects of biologybiology
EcologyEcology TerrestrialTerrestrial AquaticAquatic
CellularCellular All organisms have an optimum pH for All organisms have an optimum pH for
growthgrowth
Indicator Species-TerrestrialIndicator Species-Terrestrial
HydrangeaHydrangea
BlackberriesBlackberries
www.steepvillage.com/Blackberries.jpg
Indicator Species-AquaticIndicator Species-Aquatic
MolliesMollies
Ram CichlidRam Cichlid http://www.sbs.utexas.edu/ryan/images/mollies.gif
www.aquariumworld.com/images/micr_ramirezi.jpg
http://ic.ucsc.edu/~wxcheng/envs23/lecture17/AcidR.html
Indicator Species- CellularIndicator Species- Cellular
Pythium spp.Pythium spp.
www.cals.ncsu.edu/.../stramen/Pythium.jpg
Acids and BasesAcids and Bases
AcidsAcids are substances that dissociate are substances that dissociate in water and release hydrogen ions in water and release hydrogen ions (H(H++).).
Bases Bases are substances that either are substances that either take up hydrogen ions (Htake up hydrogen ions (H++) or release ) or release hydroxide ions (OHhydroxide ions (OH--).).
pOHpOH
Definition:Definition: pH=-log [OHpH=-log [OH--] ]
In wordsIn words The negative logarithm of the The negative logarithm of the
concentration of hydroxide ionsconcentration of hydroxide ions
AcidsAcids
Acids will be capable of giving off HAcids will be capable of giving off H++
ExamplesExamples HCL HCL H H++ + Cl + Cl--
HBr HBr H H++ + Br + Br--
http://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gif
BasesBases
Bases are capable for giving off OHBases are capable for giving off OH--.. ExamplesExamples
KOH KOH K K++ + OH + OH NaOH NaOH Na Na++ + OH + OH
http://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gif
WaterWater
Water dissociatesWater dissociates HH220 0 H H++ +OH +OH--
BuffersBuffers
Definition:Definition: A solution that resists change in pH. A solution that resists change in pH.
Takes up excess HTakes up excess H++ and OH and OH--
Even buffered solutions can change pH if Even buffered solutions can change pH if enough Henough H++ or OH or OH-- is added. is added.
Buffer examplesBuffer examples
BloodBlood HH22COCO33 H H++ + HCO + HCO33
--
http://donatebloodtoday.org/images/blood%20bags.jpg
Buffered systemBuffered system
A system (group of particles) that A system (group of particles) that can act as a buffercan act as a buffer
ExamplesExamples SoilSoil Large bodies of waterLarge bodies of water
ReviewReview
What is pH?What is pH? pH scalepH scale Effects and indicatorsEffects and indicators pOHpOH AcidsAcids BasesBases BuffersBuffers
http://www.sikeston.k12.mo.us/gwilliams/images/bases.jpg