1 / 12

Bases

Acids. and. Bases. Acid and Base Properties. *Usually, but not always. Base. Acid. Taste. Bitter. Sour. Feel (choose slippery or not slippery). Slippery. Not slippery. pH (# from the key). 8-14. 1-6. Litmus (blue or red). Blue. Red. Phenolphthalein. *Pink. *Cloudy/ white.

conan-sutton
Download Presentation

Bases

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. Acids and Bases

  2. Acid and Base Properties *Usually, but not always Base Acid Taste Bitter Sour Feel (choose slippery or not slippery) Slippery Not slippery pH (# from the key) 8-14 1-6 Litmus (blue or red) Blue Red Phenolphthalein *Pink *Cloudy/ white Bromothymol *Blue *Yellow Magnesium NR Bubbles Baking soda NR Bubbles

  3. pH • There are many ways to consider acids and bases. One of these is pH. • [H+] is critical in many chemical reactions. • A quick method of denoting [H+] is via pH. • By definition pH = –log [H+], [H+] = 10-pH • The pH scale, similar to the Richter scale, describes a wide range of values • An earthquake of “6” is 10 as violent as a “5” • Thus, the pH scale condenses possible values of [H+] to a 14 point scale • Also, it is easier to say pH=7 vs. [H+]=1x10–7

  4. Calculations with pH Q: What is the pH if [H+]= 6.3 x 10–5? pH = –log [H+] (‘6.3’, ‘exp’ or ‘EE’, ‘5’, ‘+/-’, ‘log’, ‘+/-’) (‘-’, ‘log’, ‘6.3’, ‘exp’ or ‘EE’, ‘-’, ‘5’) Ans: 4.2 Q: What is the [H+] if pH = 7.4? [H+] = 10–pH mol/L (’10’, ‘xy’, ‘7.4’, ‘+/-’, ‘=‘) (’10’, ‘^’, ‘-’, ‘7.4’, ‘=‘) 3.98x10–8 M

  5. 2 a) pH = –log [H+] = –log [1x10–8] = 8.0 b) pH = –log [H+] = –log [1x10–7] = 7.0 c) pH = –log [H+] = –log [2.5x10–6] = 5.60 d) pH = –log [H+] = –log [1.3x10–4] = 3.89 3 a) [H+] = 10–pH = 10–5.4 = 4 x 10–6 mol/L b) [H+] = 10–pH = 10–5.72 = 1.9 x 10–6 mol/L

  6. Ionization + H H O H O Cl Cl H H H • O (e.g.H2SO4) was originally thought to cause acidic properties. Later, H was implicated, but it was still not clear why CH4 was neutral. • Arrhenius made the revolutionary suggestion that some solutions contain ions & that acids produce H3O+ ions in solution. Historical views on acidsArrhenius acids and bases + + • Arrhenius acid forms H30+ (hydronium ion) • Arrhenius base forms OH- (hydroxide ion)

  7. Lewis Acid • In 1923, G. N. Lewis (yes, the Lewis structure guy) suggested a way of describing a number of reactions that did not fit the Bronsted definition of acid-base reactions, yet seemed to have some unifying structural features. He suggested: • A Lewis acidis an electron pair acceptor. • Lewis baseis an electron pair donor. • The simplest reaction is for a Lewis acid to interact with a Lewis base to give a Lewis acid/base complex: A + BA-B

  8. Lewis acid/base Example • Note several things about this reaction: • They are charge balanced - that is the total charge of all species is the same on both sides of the equations • The product is sometimes described as a Lewis "complex"

  9. + + + H H O H O Cl Cl H H H • In this idea, the ionization of an acid by water is just one example of an acid-base reaction. The Bronsted-Lowry concept conjugate acid conjugate base acid base conjugate acid-base pairs • Acids and bases are identified based on whether they donate or accept H+. • “Conjugate” acids and bases are found on the products side of the equation. A conjugate base is the same as the starting acid minus H+.

  10. Identify the acid, base, conjugate acid, conjugate base, and conjugate acid-base pairs: Practice problems HC2H3O2(aq) + H2O(l)  C2H3O2–(aq) + H3O+(aq) conjugate base conjugate acid acid base conjugate acid-base pairs OH–(aq) + HCO3–(aq)  CO32–(aq) + H2O(l) base acid conjugate base conjugate acid conjugate acid-base pairs

  11. Answers: question 18 HF(aq) + SO32–(aq)  F–(aq) + HSO3–(aq) (a) conjugate base conjugate acid acid base conjugate acid-base pairs (b) CO32–(aq)+HC2H3O2(aq)C2H3O2–(aq)+HCO3–(aq) base acid conjugate base conjugate acid conjugate acid-base pairs (c) H3PO4(aq) + OCl–(aq)  H2PO4–(aq) + HOCl(aq) conjugate base conjugate acid acid base conjugate acid-base pairs

  12. 8a) HCO3–(aq) + S2–(aq)  HS–(aq) + CO32–(aq) conjugate acid conjugate base acid base conjugate acid-base pairs 8b) H2CO3(aq) + OH–(aq)  HCO3–(aq) + H2O(l) acid base conjugate base conjugate acid conjugate acid-base pairs 11a) H3O+(aq) + HSO3–(aq)  H2O(l) + H2SO3(aq) conjugate base conjugate acid acid base conjugate acid-base pairs 11b) OH–(aq) + HSO3–(aq)  H2O(l) + SO32–(aq) conjugate acid conjugate base base acid conjugate acid-base pairs For more lessons, visit www.chalkbored.com

More Related