Acid Ionization Dissolution Constant: Ka

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Acid Ionization (Dissolution) Constant Ka

• indicates the strength of the acid.
• The larger the Ka, the stronger the acid

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Ka

• HAH2O ? H3O A
• Ka H A
• HA
  

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Base Ionization (Dissolution) Constant Kb

• indicates the strength of the base.
• The larger the Kb, the stronger the base.

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Kb

• BH2O ? HB OH
• Kb HB OH
• B

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Problem

• Determine Kb for 0.150 M solution of ammonia
  which dissociates to yield 0.0016 M OH .

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Self-Ionization

• Chemical reaction between 2 molecules of the same
  substance that produces ions.
• H2O ? H OH

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For pure water at 25C

• H OH
• 1.0 x 10 7 M.

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Ion product constant for water at 25C Kw

• Kw HOH
• (1.0 x 10 7)2
• 1.0 x 1014

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Problem

• If H 0.01M, what is OH ?

OH- 1.0 x 10-12
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Problems (p.609)

• If H1.0x1013M, OH ?
• If H1.0x107 M, OH ?
• If H1.0x103M, OH ?

OH- 1.0 x 10-1
OH- 1.0 x 10-7
OH- 1.0 x 10-11
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pH log H

• p power
• H H

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pH scale is 0 to 14

• Acidic solns pH lt 7
• Neutral pH 7
• Basic pH gt 7

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Problem

• What is H in blood if OH 2.2 x 107 M?
• What is the pH?

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pOH log OH-pH pOH 14.00

• p power
• OH OH-

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If pH 2.6, what is H?

• Antilog (-2.6) ?

H 0.0025
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What is the pH of 2.4 x 10-5 M Mg(OH)2 ?

• pH9.68

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Three groups of acids

• Binary acids
• Oxy acids
• Carboxylic acids

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Binary acids

• contain H and one other element (usually from
  group 16 or 17).
• Ex. HCl, HF, H2S, H2Se

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Oxy acids

• contain H, O and 1 other element.
• H2SO4, H3PO4, HNO3

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Carboxylic acids

• organic acids.
• carboxyl group R-COOH
• most are weak acids.
• Ex. HC2H3O2

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Naming acids binary - oxy - carboxylic

• -ide ? hydro--ic acid
• -ate ? -ic acid
• -ite ?-ous acid
• -e ? -oic acid

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Name these acids

• HNO2 HNO3
• H2SO4 H2SO3
• H2S H2CO3
• H3PO4 H3PO3

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Name these acids

• HI
• HCl
• HC2H3O2
• CH3(CH2)2COOH

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Bases

• Anions
• Amines

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Bases

• anions conj. base of acid Cl , OH , NO3
• amines contain N with an unshared pair of
  electrons CH3NH2