Unformatted text preview: er [H3O+], [OH-], pH, or pOH are known,
the other three can be obtained! (Exercise 8.3)
• Normal rain or snow has a pH between 6.5 to 5.0.
• Note that this is a “log” scale.
• Affected by concentration, nature of the acid or
base, type of solvent, and temperature Difference in Determining pH of Concentrated
and Dilute Solutions…Water!
• With strong acid or strong base, “what you see
is what you get” (ignore any H+ or OH– from
water if acid or base is concentrated).
• However, in dilute solutions of SA or SB, check
for possible contributions from water.
• Use the mass balance equation:
• [H+] = [H+]HA + [H+]water Weak Acid or Base—One More
Consideration • First, additional contributions of water to H+ and OH–
can generally be ignored if the concentration of the
acid or weak base is above ~ 10-6 M, and also if the Ka
or Kb is larger than 10-6.
• Exercise 8.4
Use the following: Weak Acids and Weak Bases...Small Ka
• Trimethylamine (Kb = 6.35 × 10–5 ) is partially
responsible for the aroma of fish. What would be the
pH of a solution with an initial concentration of
0.0557M? • N3H9N + H2O N3H9N H+ + OH- Use Kb = (P/R); Kb = [N3...
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