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ACIDS, BASES , AND pH

ACIDS, BASES , AND pH. Arrhenius ACIDS. An acid -------> H + in water. HCl( aq ) ---> H + ( aq ) + Cl - ( aq ). Arrhenius BASES. Base ---> OH - in water. NaOH ( aq ) ---> Na + ( aq ) + OH - ( aq ). NaOH is a strong base. Arrhenius Theory.

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ACIDS, BASES , AND pH

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  1. ACIDS, BASES, AND pH

  2. Arrhenius ACIDS An acid -------> H+ in water HCl(aq) ---> H+(aq) + Cl-(aq)

  3. Arrhenius BASES Base ---> OH- in water NaOH(aq) ---> Na+(aq) + OH-(aq) NaOH is a strong base

  4. Arrhenius Theory Acids H+(hydrogen ions) in water HCl → H+ + Cl- Bases OH-(hydroxide ions) in water • NaOH → Na+ + OH- D7C20

  5. Arrhenius Theory • Substances ionize in water • Acids, bases, and salts when dissolved in water, will conduct electricity. • Called Electrolytes

  6. Aqueous Solutions How do we know ions are present? The solutions conduct electricity! They are called ELECTROLYTES HCl, MgCl2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions.

  7. HNO3 ACIDS An acid -------> H+ in water Some strongacids are HCl hydrochloric H2SO4 sulfuric HClO4 perchloric HNO3 nitric

  8. Strong Acids will completely ionize

  9. Aqueous Solutions weak electrolyte, like Acetic acid, ionizes only to a small extent, CH3CO2H(aq) t CH3CO2-(aq) + H+(aq)

  10. Acetic acid Weak Acids Weak electrolytes CH3CO2H acetic acid H2CO3 carbonic acid H3PO4 phosphoric acid HF hydrofluoric acid

  11. Know the strong acids & bases!

  12. Aqueous Solutions Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes. Examples include: sugar ethanol ethylene glycol

  13. Hydrogen ions in water = Hydronium ions

  14. Ammonia, NH3An Important Base

  15. ACID-BASE THEORIES • The most general theory for common aqueous acids and bases is the BRØNSTED - LOWRY theory • ACIDS DONATE H+ IONS • BASES ACCEPT H+ IONS

  16. Bronsted Base: adds one hydrogen ion Reactants Products Bronsted Acid: removes one hydrogen ion

  17. Chemical Reactions: New products are formed

  18. Brønsted-Lowry Theory • HCl + H2O → H3O+ + Cl- acid base C.A. C.B. • Conjugate acid –the PRODUCT obtained after a BASE gains a proton (hydrogen ion) • Conjugate base –the PRODUCT obtained after an ACID donates a proton (hydrogen ion)

  19. Conjugate Pairs

  20. Amphoteric • A substance having the ability to act as an acid or a base or AmphoPROTIC Hydrogen ion = proton

  21. Water is amphoprotic It can gain and lose a H+

  22. Why is Water Neutral? [H3O+ ] = [OH-] When one water gains, another loses a H+

  23. Brønsted-Lowry Theory D7C20 • ACID: any substance that donates a proton (hydrogen ion) • BASE: any substance that accepts a proton (hydrogen ion) • MUST occur together; Can not gain unless something else loses

  24. You Practice • NH3 + H2O → NH4+ + OH- • HNO3 + NaOH → H2O + NaNO3 • NaHCO3 + HCl → NaCl + H2CO3

  25. EXCHANGE: Precipitation Reactions EXCHANGE Gas-Forming Reactions REDOX Reactions REACTIONS Acid- Base REACTIONS

  26. ACIDS Nonmetal oxides can be acids CO2(aq) + H2O(liq)--->H2CO3(aq) SO3(aq) + H2O(liq) ---> H2SO4(aq) and can come from burning coal and oil.

  27. BASES Metal oxides are bases CaO(s) + H2O(liq) --> Ca(OH)2(aq) CaO in water. Indicator shows solution is basic.

  28. Acid-Base Reactions • sometimes called NEUTRALIZATIONSbecause the solution is neither acidic nor basic at the end. • The other product of the A-B reaction is a SALT, MX. HX + MOH ---> MX + H2O Mn+ comes from base &Xn- comes from acid This is one way to make compounds!

  29. Acid-Base Reactions The “driving force” is the formation of water. NaOH(aq) + HCl(aq) ---> NaCl(aq) + H2O(liq) Net ionic equation OH-(aq) + H+(aq) ---> H2O(liq) This applies to ALL reactions of STRONG acids and bases.

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