1 / 11

Bases

Acids. and. Bases. Properties of acids and bases. Get 8 test tubes. Rinse all tubes well with water. Add acid to four tubes, base to the other four. Touch a drop of base to your finger. Record the feel in the chart (on the next slide). Wash your hands with water. Repeat for acid.

erica-shannon
Télécharger la présentation

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. Properties of acids and bases • Get 8 test tubes. Rinse all tubes well with water. Add acid to four tubes, base to the other four. • Touch a drop of base to your finger. Record the feel in the chart (on the next slide). Wash your hands with water. Repeat for acid. • Use a stirring rod, add base to the litmus and pH papers (for pH paper use a colour key to find a number). Record results. Repeat for acid. • Into the four base tubes add: a) two drops of phenolphthalein, b) 2 drops of bromothymol, c) a piece of Mg, d) a small scoop of baking soda. Record results. Repeat for acid. • Cleanup(wash tubes,pH/litmus paper in trash).

  3. PROPERTIES *Usually, but not always BASE(aq) ACID(aq) Taste Bitter Sour “Feelings” Slippery Not slippery pH >7 <7 Litmus Blue Red Phenolphthalein Pink Clear & colorless Bromothymol *Blue *Yellow Reacts w/ Metal No Yes Electrolyte (conducts electricity in H2O) Yes Yes

  4. pH • There are many ways to consider acids and bases. One of these is pH. Read pg. 368-70. • [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 (fig. 2, p370) • Also, it is easier to say pH=7 vs. [H+]=1x10–7

  5. 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 Try questions 2 and 6 (a-b) on page 375

  6. Pg. 375 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 6 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

  7. 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+ (hydronium) ions in solution. Historical views on acids + + • The more recent Bronsted-Lowry concept is that acids are H+ (proton) donors and bases are proton acceptors

  8. + + + 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+.

  9. 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 • Reference: pg. 386 – 387 • Try Q18 (p389), Q 8 & 11 (p392): do as above

  10. 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

  11. 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