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Review: Arrhenius Definition of Acids and Bases

Review: Arrhenius Definition of Acids and Bases. Acids produce H + in aqueous (water) solutions water HCl H + (aq) + Cl - (aq) Bases produce OH - in aqueous (water) solutions water NaOH Na + (aq) + OH - (aq). The Br ø nsted-Lowry Definition of Acids and Bases.

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Review: Arrhenius Definition of Acids and Bases

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  1. Review: Arrhenius Definition of Acids and Bases Acids produce H+ in aqueous (water) solutions water HCl H+ (aq) + Cl- (aq) Bases produce OH- in aqueous (water) solutions water NaOH Na+ (aq) + OH- (aq)

  2. The Brønsted-Lowry Definition of Acids and Bases Acid: PROTON DONOR can donate H+ ions. Base:PROTON ACCEPTOR acceptsH+ ions. Broader Definition than Arrhenius

  3. Acid/base reactions involve “proton transfer”. The reaction need not occur in water. H+ Transfer

  4. Follow the H+ • H+ leaves one compound and is transferred to another. Ex: NH3 + H2O NH4+ + OH- Base Acid

  5. Conjugate acid/base pairs:formulas differ by only a hydrogen ion, H+. The acid on one side becomes the base on the other side and vice versa. Ex: HCl + H2O H3O+ + Cl- Acid Base Acid Base

  6. Conjugate acid contains one more H+ in its formula

  7. Label the Conjugate Acids and Bases in Each Reaction

  8. Amphoteric/Amphiprotic Substances: Can act as either an acid or a base. Must have an “H” in formula (to donate) Must have a free e- pair (to accept a H+)

  9. Water is amphoteric • It can donate an H+ or accept an H+ • It depends on what it is combined with.

  10. Water donates H+ to NH3 forming the hydroxide ion (OH-). Water acceptsH+ from HCl forming the hydronium ion (H3O+).

  11. - H+ + H+ When it can go either way… Amphoteric (amphiprotic) substances Acting like a base Acting like an acid HCO3- H2CO3 CO3-2 accepts H+ donates H+

  12. Let’s Practice • What is the Brønsted-Lowry definition of an acid? • A substance that donates protons. • A substance that accepts protons. • A substance that dissolves in water to form ions. • A substance that dissolves in water to form ions.

  13. If H3O+ is an acid according to the Brønsted-Lowry theory, what is the conjugate base of this acid? • H4O+2(aq) • H+(aq) • H2O (l) • OH-(aq)

  14. According to one acid-base theory, water acts as an acid when an H2O molecule (1) accepts an H+  (2) accepts an H- (3) donates an H+  (4) donates an H-

  15. One acid-base theory defines a base as an (1) H+ donor        (2) H donor (3) H+ acceptor   (4) H acceptor

  16. What is the conjugate base of H2PO4- • H3O+ (aq) • H3PO4(aq) • HPO4-2(aq) • PO4-3(aq)

  17. Online tutorial on Bronsted/Lowry • http://www.sophia.org/acids-and-bases-definitions-bronsted-lowry/acids-and-bases-definitions-bronsted-lowry-tutorial

  18. Dilution water (solvent) solute moles of solute remain constant diluted, Mfinal Vfinal molesinitial = molesfinal Vinitial concentrated, Minitial adding water lowers the solute concentration Mfinal x Vfinal = Minitial x Vinitial

  19. Acid/Base Summary Films • The Proton in Chemistry http://www.learner.org/vod/vod_window.html?pid=808 Acid and Base Tutorial: http://www.youtube.com/watch?v=MzK3bDkzXq4&safe=active Acid Base Quiz http://www.sciencegeek.net/Chemistry/taters/Unit6AcidsBases.htm Acid Bases Hydrogen Transfer (Neutralization) http://preparatorychemistry.com/neutralization_flash.htm

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