Final answer:
The question requires calculating the change in pH of a buffer solution after the addition of NaOH. The moles of NaOH added are used to adjust the buffer component concentrations, after which the Henderson-Hasselbalch equation is used to find the new pH and determine the percent change in pH relative to the initial pH.
Step-by-step explanation:
The question involves calculating the percent change in pH when a certain amount of NaOH is added to a buffer solution. To solve this, we must first find the moles of NaOH added, and determine how much it will affect the concentration of the buffer components, HX and NaX.
The moles of NaOH are given by the mass divided by the molar mass, so for 4.052 g of NaOH with a molar mass of 39.997 g/mol, we have 0.1013 mol of NaOH (since 4.052g / 39.997g/mol = 0.1013 mol). When added to the buffer, NaOH will react with HX to form H2O and NaX. This will shift the buffer concentrations, as HX will decrease and NaX will increase by 0.1013 mol.
Since the buffer has a volume of 394 mL, we need to convert this to liters in order to use it in molarity calculations (0.394 L). We can then use the Henderson-Hasselbalch equation to find the new pH, and compare it to the initial pH, obtaining the absolute change and the percent change. An example given in the problem indicates that for a similar situation, the pH changed from 4.74 to 4.75, which is an insignificant change, demonstrating the buffer's ability to resist pH changes. However, the exact calculations need to be carried out for the particular quantities given in the problem to find the correct percent change in pH from the options provided.