Final answer:
To calculate the change in pH of a buffer solution after adding HCl, we consider the reaction of HCl with the acetate ions to form acetic acid, use stoichiometry to adjust the concentrations of the buffer components, and apply the Henderson-Hasselbalch equation.
Step-by-step explanation:
The question relates to the change in pH of a buffer solution after the addition of HCl. A buffer solution containing equimolar concentrations of acetic acid and sodium acetate is known to resist changes in pH when small amounts of acid or base are added. When HCl is added to the buffer, the acetate ions react with the added H+ ions to form acetic acid, thus minimizing the change in pH. The pH of the buffer before the addition of HCl is given as 4.74. To calculate the new pH after adding HCl, we need to know the number of moles of HCl added and the final concentrations of acetic acid and acetate ions in the buffer after the reaction.
To solve this, we'd use the reaction:
CH3COO- (from CH3COONa) + H+ (from HCl) → CH3COOH
Assuming that the reaction goes to completion and using stoichiometry, we can determine the changes in the molar concentrations of acetic acid and acetate ions. Then, we'd apply the Henderson-Hasselbalch equation pH = pKa + log([A-]/[HA]) to find the new pH. Since we are not given the volume for the final solution, we assume no significant volume change for this calculation, which is a reasonable assumption given the small volumes involved compared to the buffer solution.