SelfIonization of Water

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Self-Ionization of Water
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Example

• Lemon juice H 0.010 M, OH- ??

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Relation between OH- H3O

• When H3O(aq) increases, OH-(aq) decreases.
• When H3O(aq)decreases, OH-(aq) increases.
• When OH-(aq) increases, H3O(aq) decreases.
• When OH-(aq)decreases, H3O(aq) increases.

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• Acidic ? H3O ? 10-7 M
• Alkaline ? H3O ? 10-7 M
• Neutral ? H3O 10-7 M

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pH Scale
pH
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pH Chart
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Table 16.4
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pOH
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Sample Problem

• The pH of a solution is 9.40. Calculate the
  H(aq) H3O(aq) OH-(aq) and pOH.
• pH -logH(aq) logH(aq) -pH
• H(aq) antilog(-pH) 10-pH 10-9.40
• 4.0 x 10-10 M H3O(aq)
• OH-(aq) (10-14)/ H3O(aq) 10-14/ 4.0 x
  10-10
• 2.5 x 10-5 M
• pOH 14 - pH 14 - 9.40 4.60
• pOH - logOH-(aq) - log(2.5 x 10-5 M) 4.60

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For Example

• The pH of a solution is 9.29. The solution is
  basic or alkaline.
• The pH of another solution is 2.13. The solution
  is acidic.
• The pH of yet another solution is 7.00 at 25oC.
  The solution is neutral.

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pH Properties
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Measurement of pH

• pH indicators
• pH paper
• pH meter

Beckman's 1st pH meter
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Buffers

• Buffers are solutions which keep the pH of a
  solution almost constant when a strong acid or
  base are added.
• Buffers are prepared by mixing a weak acid and
  the salt of the acid or by mixing a weak base and
  the salt of the base.

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How the acetic acid/sodium acetate buffer works.

• When base (OH-) is added
• When acid (H) is added

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Buret Used in Acid-Base Titrations
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Titration

• At the end point an equivalent amount of base has
  been added. This is sometimes called the
  equivalence point.
• At the equivalence point, the moles of H in the
  acid is equal to the moles of OH- added.