CHM 104 1st Edition Lecture 14 Outline of Last Lecture I Acid Strength and the Ionization Constant Outline of Current Lecture II Strong and Weak Acid III X is small IV Calculating pH V Percent Ionization Current Lecture Strong Acid pH of 0 10M HCl Unless the HCl is 10 6 M we don t worry about ionization of H 2O Weak Acid pH of 0 10 M HC2H3O2 Solution Both K s are small but Ka for acetic acid is a billion times bigger than Kw So ASSUME most all H3O comes from H2C2H3O2 X is small when Ka 10 4 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Calculating Ka by measuring pH of solution The pH of 0 100 M HA solution is 5 00 what is the Ka H3O eq 10 pH 1 0 X 10 5M HA H2O A H3O I 0 100 0 0 C X X X E 0 100 1 0 X 10 5 1 0 X 10 5 1 0 X 10 5 Calculating concentration from pH measurement The pH of an acid with Ka 1 0 x 10 8 is 5 00 what is its concentration HA I H2O l a A0 H3O 0 C 1 0 X 10 5 1 0 X 10 5 1 0 X 10 5 E 1 0 X 10 5 1 0 X 10 5 1 0 X 10 5 H3O eq 1 0 X 10 5 Calculating ionization for an acid Important Trends H3O EQ as Ka increases H3O EQ as acid concentration increases ionization as Ka Mixtures of Acids Strategy Focus on the STRONGEST acid in the mix Calculate pH of a mixture of 0 10 M HCl and 0 10 M acetic acid Ka 1 8 x 10 5 If K s for the 2 acids differ by more than 102 then just FOCUS on the stronger acid
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