Calculate the change in pH if 0.050 g of solid NaOH is added to 250 mL of a buffer solution that contains 0.80 M NaH2PO4 and 0.17M Na2HPO4.

I found the pH of the buffer solution to be 6.54.

To calculate the change in pH when solid NaOH is added to the buffer solution, we need to consider the reaction that occurs.

The reaction between NaOH and NaH2PO4 can be represented as follows:
NaOH + NaH2PO4 → Na2HPO4 + H2O

First, determine the moles of NaOH added to the buffer solution:
Moles of NaOH = mass of NaOH / molar mass of NaOH
Molar mass of NaOH = 22.99 g/mol + 16.00 g/mol + 1.01 g/mol = 39.99 g/mol
Moles of NaOH = 0.050 g / 39.99 g/mol

Next, calculate the change in moles of NaH2PO4 and Na2HPO4 in the buffer solution:
Change in moles NaH2PO4 = -moles NaOH
Change in moles Na2HPO4 = moles NaOH

Now, determine the new concentrations of NaH2PO4 and Na2HPO4 in the buffer solution:
New concentration of NaH2PO4 = (initial moles NaH2PO4 + change in moles NaH2PO4) / (initial volume of solution + volume of NaOH added)
New concentration of Na2HPO4 = (initial moles Na2HPO4 + change in moles Na2HPO4) / (initial volume of solution + volume of NaOH added)

After calculating the new concentrations, calculate the new pH of the buffer solution using the Henderson-Hasselbalch equation:
pH = pKa + log10 ([A-] / [HA])
Where pKa is the acid dissociation constant for the buffer system, [A-] is the concentration of the conjugate base (Na2HPO4), and [HA] is the concentration of the acid (NaH2PO4).

Finally, calculate the change in pH by subtracting the new pH from the initial pH.

Given that the initial pH of the buffer solution is 6.54, the calculated change in pH after adding NaOH will be the difference between the new pH and 6.54.