3. One form of Henderson-Hasselbalch Equation shown below (See also Chapter 19.4 and 26.3) can be derived from the generic equation for an acid-dissociation reaction. It is useful for approximating the pH of an aqueous buffer. The expression can also be arranged to solve for pKa or the ratio of [conjugate base]:[acid] or [base]:[conjugate acid] depending on the functional group being ionized. Consider the two different cases below. Decide if the compound shown is most likely acting as a base or acid then draw the most likely ionized form of the compound as it would exist at pH 7. For each case calculate the % ionization. Using the appropriate form of the Henderson-Hasselbalch expression, show your work which led to each % ionized answer. (2pts for each correct structure, 1pt for each correct % ionization, 4pts for relevant work shown). Note: You will need to use Table 1.8 in your text to find the relevant pKa. Round the pKa to the nearest whole number.

pKa thiols = 10.7 => 11

pKa water = 15.7 => 16

3. One form of Henderson-Hasselbalch Equation shown below (See also Chapter 19.4 and 26.3) can be derived from the generic equation for an acid-dissociation reaction. It is useful for approximating the pH of an aqueous buffer. The expression can also be arranged to solve for pKa or the ratio of [conjugate base]: [acid] or [base]:[conjugate acid] depending on the functional group being ionized. Ka derivation HA + H + Lao pH = pka + log HA Acid Dissociation Reaction Henderson-Hasselbalch Eqn. (solving for pH) Consider the two different cases below. Decide if the compound shown is most likely acting as a base or acid then draw the most likely ionized form of the compound as it would exist at pH 7. For each case calculate the % ionization. Using the appropriate form of the Henderson-Hasselbalch expression, show your work which led to each % ionized answer. (2pts for each correct structure, 1pt for each correct % ionization, 4pts for relevant work shown). Note: You will need to use Table 1.8 in your text to find the relevant pKa. Round the pKa to the nearest whole number. Case 1: pH = 7 SH unionized form % ionized at pH = 7 most likely ionized form Case 2: pH = 7 % ionized at pH = 7 unionized form most likely ionized form Show work for how you solved for the % ionization below: 3. One form of Henderson-Hasselbalch Equation shown below (See also Chapter 19.4 and 26.3) can be derived from the generic equation for an acid-dissociation reaction. It is useful for approximating the pH of an aqueous buffer. The expression can also be arranged to solve for pKa or the ratio of [conjugate base]: [acid] or [base]:[conjugate acid] depending on the functional group being ionized. Ka derivation HA + H + Lao pH = pka + log HA Acid Dissociation Reaction Henderson-Hasselbalch Eqn. (solving for pH) Consider the two different cases below. Decide if the compound shown is most likely acting as a base or acid then draw the most likely ionized form of the compound as it would exist at pH 7. For each case calculate the % ionization. Using the appropriate form of the Henderson-Hasselbalch expression, show your work which led to each % ionized answer. (2pts for each correct structure, 1pt for each correct % ionization, 4pts for relevant work shown). Note: You will need to use Table 1.8 in your text to find the relevant pKa. Round the pKa to the nearest whole number. Case 1: pH = 7 SH unionized form % ionized at pH = 7 most likely ionized form Case 2: pH = 7 % ionized at pH = 7 unionized form most likely ionized form Show work for how you solved for the % ionization below