1. pH Gary Bates University of Arkansas

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

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

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

5. Log info Logarithm- Logarithm- Inverse of exponential Inverse of exponential ten fold differences between numbers ten fold differences between numbers Difference in Difference in pH of 1 & 2 pH of 1 & 2 pH of 1 & 3 pH of 1 & 3 pH of 6 & 3 pH of 6 & 3 Concentration Concentration pH of 7 pH of 7 10 7 H + 10 7 H + http://en.wikipedia.org/wiki/Logarithm

6. Definition:Acids and Bases Acids are substances that dissociate in water and release hydrogen ions (H + ). 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 - ). 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. pH scale used to indicate acidity and basicity of a solution. Ranges from 0-14 Ranges from 0-14 7 = Neutral 7 = Neutral >7 = Base >7 = Base <7 = Acid <7 = Acid Logarithmic Scale 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 pH is important in most aspects of biology Ecology Ecology Terrestrial Terrestrial Aquatic Aquatic Cellular Cellular All organisms have an optimum pH for growth All organisms have an optimum pH for growth

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

11. Indicator Species-Aquatic Mollies Mollies Ram Cichlid 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. 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 + ). 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 - ). Bases are substances that either take up hydrogen ions (H + ) or release hydroxide ions (OH - ).

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

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

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

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

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

20. Water Water dissociates Water dissociates H 2 0  H + +OH - H 2 0  H + +OH -

21. Buffers Definition: Definition: A solution that resists change in pH. Takes up excess H + and OH - 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 Blood H 2 CO 3  H + + HCO 3 - H 2 CO 3  H + + HCO 3 - http://donatebloodtoday.org/images/blood%20bags.jpg

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

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

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