CHM 104 1st Edition Lecture 15 Outline of Last Lecture I Strong and Weak Acid II X is small III Calculating pH IV Percent Ionization Outline of Current Lecture V Solutions Containing Bases VI Calculating pH VII Base Ionization Constant VIII Classifying Compounds Current Lecture Solutions containing Bases Calculating pH The Strong Bases are all Strong Electrolytes Group 1A Group 2A LiOH Ca OH 2 NaOH Ba OH 2 KOH Sr OH 2 metal hydroxides Strong Base pH of 0 100 M NaOH solution OH 0 100 M pOH log 0 100 1 00 pH 14 1 00 13 00 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 Strong Base pH of 0 100 M Ca OH 2 solution H3O Kw OH 1 0x10 14 0 200 5 00x10 14 pH 13 30 Weak Bases Produce OH by Accepting H from H2O The extent is characterized by Base Ionization Constant The smaller Kb is the weaker the Base is Calculating the pH of a 0 100 M NH3 solution Classifying compounds as acids bases or neutral Consider NaF s strong electrolyte Group I and Group II are neutral species Li Ca2 K Mg2 Na Ba2 Conjugates of Strong Bases They have no effect on pH F is the conjugate base to HF Solution should be basic What is the value of Kb Ka x Kb constant If Ka for an acid is big then Kb for the conjugate base is small strong weak acid weak weak base There is an inverse relationship between the strength of a weak acid and the strength of its conjugate base Increasing Strength HCl strong Cl Negligible HF Ka 3 5 x 10 4 F Kb 2 9 x 10 11 HC2H3O2 Ka 1 8 x 10 5 C2H3O2 Kb 5 5 x 10 10 H C2H8N2 Ka 1 2 x 10 10 C2H8N2 Kb 8 3 x 10 5 Na Negligible OH strong Increasing Strength Calculate pH of 0 100M NH4Cl I I 0 0 X I X X E 0 100 X I X X C 0 100 M Ka Kw Kb NH3 1 0 X 10 14 1 8 X 10 5 5 5 X 10 10 Ka 5 5 X 10 10 X2 0 100 X 7 4 X 10 6 M H3O pH 5 13 Summary of Neutral ions Cations conjugates of Strong Bases Na K Li Ca2 Ba2 Sr2 Anions conjugates of Strong Acids Cl Br I NO3 ClO4Whether a solution is acidic or basic depends on their relative strengths NH4 Ka 5 5 x 10 10 F Kb 2 9 x 10 11 1 Salts in which neither cation nor anion acts as an acid or base form pH neutral solutions 2 Salts in which the cation does not act as an acid and the anion acts as a base form basic solutions 3 Salts in which the cation acts as an acid and the anion does not act as a base form acidic solutions 4 Salts in which cations act as an acid and the anion acts as a base for solutions in which pH depends on the relative strengths of the acid and the base
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