Final answer:
The concentration of the HCl solution affects the rate of pH change during the titration of the NaOH solution. A higher concentration of HCl results in a more rapid decrease in pH as the equivalence point is approached.
Step-by-step explanation:
The concentration of the HCl solution affects the titration of the NaOH solution. In a titration, a solution of known concentration (titrant) is added to a solution of unknown concentration (analyte) until the reaction between the two is complete. The concentration of the HCl solution determines the amount of HCl available to react with the NaOH solution, which affects the pH change during the titration.
When a higher concentration of HCl is used, more HCl molecules are available to react with the NaOH molecules. As a result, the pH of the solution decreases more rapidly as the equivalence point is approached. On the other hand, when a lower concentration of HCl is used, fewer HCl molecules are available to react, resulting in a slower decrease in pH as the equivalence point is approached.
Therefore, the concentration of the HCl solution directly affects the rate of pH change during the titration of the NaOH solution.