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Bases

Acids. and. Bases. Ionization. +. H. Cl. Cl. H. Oxygen (e.g. H 2 SO 4 ) was originally thought to cause acidic properties. Later, Hydrogen was implicated, but it was still not clear why CH 4 was neutral.

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Bases

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  1. Acids and Bases

  2. Ionization + H Cl Cl 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 H+ 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

  3. + + + 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+.

  4. 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

  5. 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.

  6. 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? • Reference: pg. 488-491 • Try questions 1,2 on page 492

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