A 1.982g sample of N-2-acetamido-2-aminoethane-sulfonic acid potassium salt ( ACES−K+, MW = 220.29 g/mol) is dissolved in 87.51 mL of water.To the solution, 21.98 mL of HCl is added, resulting in a pH of 7.27. Calculate the concentration of the HCl solution. The p?a of ACES is 6.85.
I have calculated this several times and have gotten the same answer, 0.112754 M. However, Sapling says that I am wrong. Then Sapling gives these instructions:
To begin, calculate the original number of moles of ACES− in solution. When a strong acid, such as HCl, is added to a weak base, such as ACES−, the HCl will react completely and ACES− will be converted to ACES. The number of moles of H+ added equals the number of moles of ACES− consumed, which is equal to the corresponding increase in the moles of ACES in solution. Write the reaction between ACES− and HCl and set up a table showing the initial and final number of moles of ACES− and ACES in solution after the addition of ? number of moles of HCl. Use the Henderson-Hasselbalch equation to determine the moles of HCl added to the solution.
I have attempted this and still do not have the correct answer. Please and thank you to whoever knows how to do this.