1 / 24

Have you ever… Drank tea? Been bitten by an ant? Eaten a tomato?

Tannic acid. Have you ever… Drank tea? Been bitten by an ant? Eaten a tomato? What do these three things have in common? ACID!. http://bwrc.eecs.berkeley.edu/People/Grad_Students/huifangq /food/HuifangCookings/edited/tea.jpg. Formic acid.

kanan
Download Presentation

Have you ever… Drank tea? Been bitten by an ant? Eaten a tomato?

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. Tannic acid Have you ever… • Drank tea? • Been bitten by an ant? • Eaten a tomato? • What do these three things have in common? ACID! http://bwrc.eecs.berkeley.edu/People/Grad_Students/huifangq /food/HuifangCookings/edited/tea.jpg Formic acid http://www.cogsci.indiana.edu/farg/harry/bio/zoo/ant.jpg Ascorbic acid http://upload.wikimedia.org/wikipedia/en/thumb/0/0e/Tomato2.jpg/250px-Tomato2.jpg

  2. What are acids? • What defines an acid in a chemical formula? • Write H first in the formula!!! Ex. H2SO3(aq) HC2H3O2 (aq) SULFITE ACETATE SULFUROUS ACID ACETIC ACID

  3. Properties of Acids and Bases AcidsBases • To the skin… Corrosive Corrosive • Taste Sour Bitter • Feels --- Slippery (soap) • Electrolytes Yes Yes • pH <7 >7 • Litmus paper Turns red Turns blue • Reacts With basesWith acid To form salt and water • React w/metals Make H2 No rxn • React w/ (CO3-2) Form CO2,H2O, salt No rxn

  4. Theories of Acids and Bases Limitations: • aqueous solutions • only applies to bases with OH-

  5. Theories of Acids and Bases +1 -1 H H H – N : + H – O : H – N – H + : O : H H H H .. .. From Arrhenius point of view, NH3 is a … TILT! From B-L point of view, NH3 is a … base. From Lewis point of view, NH3 is a … base.

  6. ionization • What happens when 2 water molecules react? auto-ionization - two water molecules react to produce a hydronium (H3O+) and a hydroxide ion (OH-):

  7. Self-ionization of water • All aqueous solutions contain both hydrogen and hydroxide ions due to self-ionization of water. • About 1 molecule of water out of 550 000 000 will dissociate. • This amounts to 1g H+ and 17g OH- in 10 000 000 L of water.

  8. Oh water • Water is special …..I mean Amphoteric! • Amphoteric – a substance that acts as either acid or base, depending on what it reacts with. • Ex. Water (most common)

  9. Acids • Hydrogen ions never actually exist in water solution because... • they are immediately attracted to a polar water molecule forming a hydronium ion.  HCl H+ H+ + Cl-  H2O H3O+ + H+

  10. Dissociation of acids

  11. Acid Strength Defined by equilibrium position of its dissociation reaction HA  H+ + A-

  12. Acid Dissociation Hydronium ion • In general… • HA + H2O A-+ H3O+ Conjugate Base Conjugate Acid Base Acid Conjugate Pair Conjugate Pair Conjugate acid-base pair Two substances related to each other by donating and accepting a single proton

  13. Acid Dissociation acid dissociation constant [A-][H3O+] [HA][H2O] Ka= = (l) [H+][A-] [HA] Ka= HA  H+ + A- AcidProtonConjugate base

  14. Dissociation Constants: Strong Acids

  15. Dissociation Constants: Weak Acids

  16. Dissociation of bases • Produces hydroxide ions (OH-) when it dissolves in water • NaOHNa+ and OH-

  17. 14.3 pH Scale pH and pOH pH = -log10[H+] pOH = -log10[OH-] Finding [H+], [OH-] from pH, pOH [H+] = 10-pH [OH-] = 10-pOH Relationship between pH and pOH [H+] [OH-] = 10 -14 pH + pOH = 14

  18. Neutral solutions Q: What is a neutral solution? • Neutral solution: any solution where the [H+] = [OH-] are equal • Basic solution : [H+] < [OH-] • Acidic solution : [H+] > [OH-]

  19. Acid –Base Indicators • What is an acid-base indicator? • A properly selected acid-base indicator can be used to visually "indicate" the approximate pH of a sample. • Acid-Base indicators are dyes that are themselves weak acids and bases.  • Acid –Base indicator- substances change color in response to acid or base. 

  20. Different indicators • Litmus - a dye that changes color (usually paper). • Phenolphthalein-- a liquid that changes color • Approximate pH range for color change: 8.0-9.8Color of acid form: clearColor of base form: red-violet

  21. indicators • pH paper --a mixture of different indicators that change colors at different pH's.  • Bromthymol blue • Approximate pH range for color change: 6.0-7.6Color of acid form: yellowColor of base form: blue

  22. Indicators • Universal indicator: solution that produces different colors for a pH range 1-12

  23. Ch 19 Shopping List • 3 Acid-Base theories • “4Acids are losers, 4Bases are winners.” –Hsekmar Nahtanagner • Properties of As and Bs • Conjugate A-B pairs • Amphoteric; auto-ionization of water • pH, pOH, [H+], [OH-] calculations • MAVA = MBVB • Weak vs. strong • Acid + Base  Salt + Water

More Related