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March 15 th Part I

March 15 th Part I. Return Papers Acids, Bases, pH, Buffer Notes Acids, Bases video Lab 7: Acids, Bases, pH and Buffers Acids and Bases Handout Break. Acids and Bases. Chapter 2 pp. 39-41 Also pp. 1008-1010. Oxygen (O) (8p + ,8n 0 ,8e - ) 2 electrons + 6 electrons. 3.

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March 15 th Part I

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  1. March 15th Part I • Return Papers • Acids, Bases, pH, Buffer Notes • Acids, Bases video • Lab 7: Acids, Bases, pH and Buffers • Acids and Bases Handout • Break

  2. Acids and Bases Chapter 2 pp. 39-41 Also pp. 1008-1010

  3. Oxygen (O) (8p+,8n0,8e-) 2 electrons + 6 electrons 3

  4. Special Properties of Water 4

  5. What is pH? A scale from the range of 0 – 14 7.0 represents neutral Lower than 7 is acid Higher than 7 is alkaline Measurement scale is logarithmic pH is the concentration of H+ More H+ the lower the pH or more acid Less H+ the higher the pH or more alkaline 5

  6. The pH Scale Acid and Base 6

  7. Note that each decrease in pH by one pH unit means a tenfold increase in the concentration of hydrogen ions. Note that each increase in pH by one pH unit means a tenfold decrease in the concentration of hydrogen ions. pH SCALE 0 7 14 acid neutral alkaline High H+, Low pH Low H+, High pH 7

  8. Hydrogen Hydrogen ion H H+ 8

  9. Fig. 2.13 in text As the Hydrogen ion concentration increases, the Hydroxyl ion concentration decreases 9

  10. Neutralization • Mixing acids and bases • Displacement reaction to form a water and a salt • HCL + NaOH NaCl + H20

  11. DISSOCIATION OF NaCl 11

  12. Carbonic acid (Weak Acid) Hydrochloric Acid (Strong Acid) 12

  13. Strong vs. Weak Acids • Weak Acids • Carbonic Acid: H2CO3 • Do not dissociate completely in water • Do not change pH • Important in buffer systems (tie up OH- ions) • Strong Acids • Hydrochloric Acid: HCL • Dissociate completely and irreversibly in water • Dramatically change pH of a solution

  14. Strong vs. Weak Bases • Weak Bases • Sodium Bicarbonate: NaHCO3 • Do not dissociate completely in water • Do not change pH • Important in buffer systems (tie up H+ ions) • Strong Bases • Sodium Hydroxide: NaOH • Dissociate completely and irreversibly in water • Dramatically change pH of a solution

  15. EQUILIBRIUM A + B AB 15

  16. Buffers resist abrupt changes in pH Buffers release H+ as pH rises They bind H+ when pH decreases Acidity only reflects FREE hydrogen ions (H+) not when they are bound to anions. HCl H+ + Cl- STRONG ACID WEAK ACID HAc H+ + Ac- NaOH Na+ + OH- STRONG BASE OH- + H+ = H2O 16

  17. THE BICARBONATE ION The most important single buffer in human blood is the bicarbonate ion Bicarbonate, HCO3-, is in equilibrium with H2CO3 (carbonic acid) as follows: Response to rise in pH H2CO3 HC03- + H+ Response to drop in pH 17

  18. Buffers protect against shifts in pH Bicarbonate buffer system Response to a rise in pH H2CO3 HCO3- + H+ Carbonic acid bicarbonate HCO3- + H+ H2CO3 bicarbonate Carbonic acid Response to a drop in pH H2CO3 H2O + CO2 Carbonic acid 18

  19. 19

  20. Range of Arterial pH Values 20

  21. Normal Balance Between Acid and Base

  22. Faucet and Drain Analogy • The blood's pH is normally between 7.35 and 7.45. • The body's goal is a constant balance between incoming/produced acids and bases (faucet on) and eliminated acids and bases (drain open). • Imbalances lead to acidosis or alkalosis (acid or base overflow in the sink) • How can the balance be maintained ?

  23. Any disease orcondition that affects the lungs, kidneys, metabolism or breathing has the potential to cause acidosis or alkalosis.

  24. Causes of Acidosis • Increased acid production within the body • Consumption of substances that are metabolized to acids, • Decreased acid excretion, • Increased excretion of base.

  25. Causes of Alkalosis • Electrolyte disturbances • prolonged vomiting or severe dehydration, • administration or consumption of base, • Hyperventilation (increased CO2 production changes the pH)

  26. Effects of Acidosis and Alkalosis • Alkalosis (pH above 7.8) • Overexcited nervous system • Muscle tetany • Nervousness • Convulsions • Death from respiratory arrest • Acidosis (pH below 7.0) • Depressed nervous system • Coma and Death

  27. Homeostasis of Acid-Base Balance • Kidneys and Lungs • Chemical Systems • Blood Buffers include: • Hemoglobin • Bicarbonate • Phosphates • Plasma Proteins

  28. pH and H+ concentrations of Body Fluids 29

  29. More on Acid-Base Balance • Text pp. 1008-1010 • Chemical Buffering Systems • Bicarbonate • Phosphate • Protein

  30. Buffer Lab • Objectives: • Understand how buffers work and determine the optimal buffering range for specified buffers • Understand the role buffer concentration plays in maintaining pH

  31. Lab # 7 • Exercise I • Determination of pH • Exercise II • Analysis of different buffers • Part I: Buffer an Acid • Part II: Buffer a Base • Group 1 will test deionized water, 100 mM Acetate Buffer and 100 mM Glycine Buffer • Group 2 will test different buffer concentrations

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