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Bases

Acids. and. Bases. Properties of Acids and Bases. *Usually, but not always. NaOH(aq). HCl(aq). Taste. Bitter. Sour. Feel. Slippery. Not slippery. pH. 14. 1. Litmus. Blue. Red. Phenolphthalein. *Pink. *Cloudy/ white. Bromothymol. *Blue. *Yellow. Magnesium. NR. Bubbles.

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Bases

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  1. Acids and Bases

  2. Properties of Acids and Bases *Usually, but not always NaOH(aq) HCl(aq) Taste Bitter Sour Feel Slippery Not slippery pH 14 1 Litmus Blue Red Phenolphthalein *Pink *Cloudy/ white Bromothymol *Blue *Yellow Magnesium NR Bubbles Baking soda NR Bubbles

  3. Ionization + H H O H O Cl Cl H H H • Oxygen (e.g. H2SO4) was originally thought to cause acidic properties. Later, Hydrogen 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

  4. + + + 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+.

  5. 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. 528-532 • Try questions 1-3 on page 532

  6. Amphiprotic • Sometimes a molecule can donate a proton (act as an acid) and sometimes it can accept a proton (act as a base). • Molecules that have this ability to act as both an acid and a base are called amphotericor amphiprotic. • Water is the most common example of an amphoteric substance.

  7. Practice For each of the following reactions identify any Bronsted-Lowry acids and bases. • HNO3 + H2O  H3O+ + NO3- • HNO3 + NH3 NH4+ + NO3- • S2- + H2O  HS- + OH- • HS- + OH- S2- + H-OH • HS- + HCl  H2S + Cl- Are any of the substances above amphoteric?

  8. Autoionization of Water • Experiments have revealed that water reacts with itself in an acid/base manner. • [H+] = [OH-] = 1.0x10-7 mol/L @ SATP

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