Water, Acids, Bases and Buffers

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Water, Acids, Bases and Buffers
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Structure and Geometry of Water

• Water is polar

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• Max. of H-bonds with other water molecules 4

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Properties of Water

• Cohesive
• High specific heat
• High heat of vaporization
• Expands when it freezes
• Is a good solvent

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Dissociation of Water

• 1 out of 554,000,000 water molecules dissociates
  at 25 C
• H OH- 1.0 x 10-7 M

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pH Scale

• pH -log10H
• H 10-7 then pH 7
• H x OH- 10-14
• If H 10-9 then OH- 10-5
• pH 9, pOH 5

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Buffers

• Weak acids or bases
• Minimize changes in pH
• Control chemical reactions
• Maintain homeostasis

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Bicarbonate Buffer System

• Major buffer system in the blood
• Keeps blood pH between 7.38 and 7.42

• HCO3- bicarbonate (weak base)
• H2CO3 carbonic acid (weak acid)