Convert 10g of NaOH to moles using the molar mass.
10 g NaOH / 39.997 g/mol NaOH = 0.25 mol NaOH
NaOH is a strong base so it dissolves completely in solution, so you’ll have 0.25 mol of OH-. Calculate the molarity of OH-.
0.25 mol OH / 0.250 L = 1.0 M OH-
Calculate the pOH. pOH = -log(1.0) = 0
pH = 14 - pOH = 14
