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Gary Bates University of Arkansas

pH. Gary Bates University of Arkansas. Review outline. Basic chemistry Orbitals Ions Molecules Properties of water. Outline. What is pH? pH scale Effects and indicators pOH Acids Bases Buffers Review. pH. Definition:* pH=-log [H + ] In words

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Gary Bates University of Arkansas

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  1. pH Gary Bates University of Arkansas

  2. Review outline • Basic chemistry • Orbitals • Ions • Molecules • Properties of water

  3. Outline • What is pH? • pH scale • Effects and indicators • pOH • Acids • Bases • Buffers • Review

  4. pH • Definition:* • pH=-log [H+] • In words • The negative logarithm of the concentration of hydronium ions

  5. Log info • Logarithm- • Inverse of exponential • ten fold differences between numbers • Difference in • pH of 1 & 2 • pH of 1 & 3 • pH of 6 & 3 • Concentration • pH of 7 • 107 H+ http://en.wikipedia.org/wiki/Logarithm

  6. Definition:Acids and Bases • Acids are substances that dissociate in water and release hydrogen ions (H+). • Bases are substances that either take up hydrogen ions (H+) or release hydroxide ions (OH-).

  7. pH Scale • pH scale used to indicate acidity and basicity of a solution. • Ranges from 0-14 • 7 = Neutral • >7 = Base • <7 = Acid • Logarithmic Scale www.greenair.com/images/tt3.gif

  8. http://staff.jccc.net/PDECELL/chemistry/phscale.html

  9. Importance • pH is important in most aspects of biology • Ecology • Terrestrial • Aquatic • Cellular • All organisms have an optimum pH for growth

  10. Indicator Species-Terrestrial • Hydrangea • Blackberries www.steepvillage.com/Blackberries.jpg

  11. Indicator Species-Aquatic • Mollies • Ram Cichlid http://www.sbs.utexas.edu/ryan/images/mollies.gif www.aquariumworld.com/images/micr_ramirezi.jpg

  12. http://ic.ucsc.edu/~wxcheng/envs23/lecture17/AcidR.html

  13. Indicator Species- Cellular • Pythium spp. www.cals.ncsu.edu/.../stramen/Pythium.jpg

  14. Acids and Bases • Acids are substances that dissociate in water and release hydrogen ions (H+). • Bases are substances that either take up hydrogen ions (H+) or release hydroxide ions (OH-).

  15. pOH • Definition: • pH=-log [OH-] • In words • The negative logarithm of the concentration of hydroxide ions

  16. Acids • Acids will be capable of giving off H+ • Examples • HCL  H+ + Cl- • HBr  H+ + Br-

  17. http://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gifhttp://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gif

  18. Bases • Bases are capable for giving off OH-. • Examples • KOH  K+ + OH • NaOH  Na+ + OH

  19. http://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gifhttp://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gif

  20. Water • Water dissociates • H20  H+ +OH-

  21. Buffers • Definition: • A solution that resists change in pH. Takes up excess H+ and OH- Even buffered solutions can change pH if enough H+ or OH- is added.

  22. Buffer examples • Blood • H2CO3 H+ + HCO3- http://donatebloodtoday.org/images/blood%20bags.jpg

  23. Buffered system • A system (group of particles) that can act as a buffer • Examples • Soil • Large bodies of water

  24. Review • What is pH? • pH scale • Effects and indicators • pOH • Acids • Bases • Buffers

  25. http://www.sikeston.k12.mo.us/gwilliams/images/bases.jpg

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