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