1 / 32

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.

judith
Download Presentation

March 15 th Part I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related