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ACIDS, BASES, and BUFFERS

ACIDS, BASES, and BUFFERS. In Biological Systems. Water Dissociation. Pure water contains only H 2 O molecules Occasionally H 2 O molecules react with each other One H 2 O molecule transfers a H + ion to the other H 2 O molecule

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ACIDS, BASES, and BUFFERS

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  1. ACIDS, BASES, and BUFFERS In Biological Systems

  2. Water Dissociation • Pure water contains only H2O molecules • Occasionally H2O molecules react with each other • One H2O molecule transfers a H+ ion to the other H2O molecule • This produces an OH- (hydroxide) ion and an H3O+ (hydronium) ion http://biology.clc.uc.edu/courses/bio104/atom-h2o.htm

  3. HYDRONIUM ION http://www.jasra.com/hydrosciences.htm • The hydronium ion gives rise to the properties of acidic solutions (sour taste, electrical conductivity, turn blue litmus red) • Acids are substances that increase the concentration of H3O+(aq) when dissolved in water and that have at least one ionizable hydrogen atom in their chemical structure

  4. FORMATION OF HYDROCHLORIC ACID The equation describes the reaction of hydrogen chloride with water to produce hydrochloric acid http://www.chemistryland.com/CHM151W/04-Solutions/acids/AcidsBases151.html

  5. HYDROXIDE ION http://www.worsleyschool.net/science/files/pH/page.html • The hydroxide ion has the properties of a base (bitter taste, slippery feel, electrical conductivity, turn red litmus paper blue) • Bases are substances that increase the concentration of OH-(aq) ions in solution

  6. Bases can be formed in one of two ways: Ionic Bases Other Bases • Combine with H+ from water directly EX. NH3(g) + H2O(l) →NH4+ (aq) + OH-(aq) • Dissociate in water to produce OH- ions directly EX. NaOH(s) →Na+(aq) + OH- (aq)

  7. NEUTRALIZATION REACTION • A reaction which occurs when an acid is mixed with a base • Water and salt are produced http://nobel.scas.bcit.ca/chem0010/unit10/10.4_neutralization.htm http://www.all-about-ph.com/acids-and-bases.html

  8. pH http://www.epa.gov/acidrain/education/site_students/phscale.html • The acidity of an aqueous solution may be expressed in terms of hydronium ion concentration http://chem-guide.blogspot.com/2010/04/ionization-of-water-ph-and-ph-scale.html • Any aqueous solution with pH = 7 will be neutral, indicating a balance of hydronium and hydroxide ions • Solutions whose pH is less than 7 are acidic • Solutions with pH greater than 7 are basic

  9. Strong and Weak Acids and Bases • Acids and bases may be classified as strong or weak, according to the degree to which they ionize when dissolved in water • Strong acids and bases ionize completely, weak ones only partially ionize • http://wikis.lawrence.edu/display/CHEM/Acids+and+Bases-Davis

  10. EQUILIBRIUM http://sowl.cengage.com/ebooks/vining_owlbook_prototype/ebook/ch16/Sect16-3-a.html • Weak acid and base equations tend to be reversible • When the opposing reactions (forward and reverse) occur at equal rates the reaction is in equilibrium

  11. pH and LIVING ORGANISMS • The components of living cells and the internal environments of multicellular organisms are sensitive to pH levels • Most cellular processes operate best at pH7

  12. BUFFERS • http://www.chemcollective.org/buffers/buffers3.php • Living systems use buffers to resist significant changes in pH • In living systems buffers usually consist of conjugate acid-base pairs in equilibrium • http://www.ehow.co.uk/video_4801918_buffer-solution-work_.html

  13. Conjugate Acids and Bases • Bronsted-Lowry acids are defined as substances that can transfer a proton (hydrogen ion) to another substance. In short, they are proton donors. • Bronsted-Lowry bases are defined as substances that can accept a proton (hydrogen ion) from another substance. In short, they are proton acceptors • http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/Acid/Bronsted_Concept_of_Acids_and_Bases

  14. Important Buffer • The most important buffer in human extracellular fluid is carbonic acid – bicarbonate • Produced when carbon dioxide reacts with water http://oceanexplorer.noaa.gov/okeanos/explorations/10index/background/edu/purpose.html

  15. Blood pH • When H+ ions enter the bloodstream the bicarbonate ions react with the H+ ions to produce carbonic acid • If a base enters the blood and removes H+ ions, carbonic acid ionizes to replace the missing H+ ions in the blood • Together the carbonic acid (conjugate acid) and bicarbonate ions (conjugate base) help maintain the pH of the blood at about 7.4

  16. THE END

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