NR 150 1st Edition Final Exam Study Guide Lectures 27 34 Lecture 27 April 1 What does the value of the acid dissociation constant represent The acid dissociation constant Ka represents the strength of an acid The higher the percent of dissociation the larger the value of Ka and the stronger the acid The lower the percent of dissociation the smaller the value of Ka and the weaker the acid What is the expression for Ka A H3O K a What is the major trend in percent ionization What represents the percent ionization of the acid at equilibrium As the concentration of a weak acid decreases the percent ionization increases At equilibrium the percent ionization is represented by H What does the value of the base dissociation constant represent The base dissociation constant Kb represents the strength of a base The higher the percentage of a base accepting H from water the larger the Kb and the stronger the base The lower the percentage of a base accepting H from water the smaller the Kb and the weaker the base Lecture 28 April 3 What is a polyprotic acid A polyprotic acid is an acid with more than one ionizable proton The second dissociation is usually neglected because they aren t significant sources of H3O Lecture 29 April 6 What kind of salts yield neutral solutions Salts that consist of an anion from a strong acid and the cation of a strong base yield neutral solutions What kind of salts yield acidic solutions Salts that cosist of the anion of a strong acid and the cation of a weak base yield acidic solutions What kind of salts yield basic solutions Salts that consist of the anion of a weak acid and the cation of a strong base yield a basic solution Predicting Acid Base Properties of Salts How can Ka and Kb be related to each other The can be related to each other through the Kw expression Lecture 30 April 8 What does the net direction of an acid base reaction depend on The net direction of an acid base reaction depends on the relative strength of the acids and bases involved A reaction will favor the formation of the weaker acid and base What is the strongest acid in water Strongest base H3O OHLecture 31 April 10 What are the steps to solving problems involving weak acid base equilibria 1 Write the balanced equation 2 Write an expression for Ka or Kb 3 Define x as the change in concentration that occurs during the reaction 4 Construct a reaction table in terms of x 5 Make assumptions to simplify the calculation 6 Substitute values into Ka Kb and solve for x 7 Check that the assumptions are justified What is an acid base titration An acid base titration is the neutralization of an acid or base of know concentration in order to determine the unknown concentration of an acid or base What is the equivalence point of a titration The end point The equivalence point of a titration is when the number of moles of OH added equals the number of moles of H3O initially present in the solution The end point is when the indicator changes color usually indicating that the titration is complete Lecture 32 April 13 What is the Henderson Hasselbalch equation pH pKa log base acid When can the Henderson Hasselbalch equation be used In equations regarding buffers or weak acids and strong bases Lecture 33 April 15 What trends can be seen in a curve for a strong acid strong base titration The pH increases gradually when excess base is added The pH rises very rapidly at the equivalence point pH 7 00 The initial pH is low Lecture 34 April 17 What trends can be seen in a curve for weak acid strong base titrations The initial pH is higher than for the strong acid solution The pH at equivalence point is more than 7 00 due to the reaction of the conjugate base with water The pH increases slowly beyond the equivalence point The curve rises gradually in the buffer or common ion region the weak acid and conjugate base are both present in the solution