You prepare a buffer solution from 10.0 mL of 0.100 M MOPS(3-morpholinopropane-1-sulfonic acid) and 10.0 mL of 0.079 M NaOH.Next, you add 1.00 mL of 5.67 × 10^-5 M lidocaine to this mixture.Denoting lidocaine as L, calculate the fraction of lidocainepresent in the form LH+.
MOPS Ka = 6.3 × 10^–8.
Lidocaine Kb = 8.7 × 10^–7
(Hint: First calculate the pH of the solution from the amount ofMOPS added. Start by finding the number of moles (or millimoles) ofHA and OH–. Which reactant is limiting? Next, find the amount of A–that forms and the amount of HA left over. Finally, determine the[A–]/[HA] ratio and use the Henderson-Haselbalch equation to findpH. The concentration of lidocaine is too low to affect this pHvalue. Calculate the pKa of lidocaine and then the fraction in theprotonated form from the pH and the pKa using the HendersonHasselbalch equation.)
