0.5123 g KHP sample was dissolved in about 25 mL of distilled water, and titrated to the phenolphthalein endpoint with 28.75 mL of a sodium hydroxide solution. Calculate the molar concentration of the hydroxide solution

Answer 1

KHP + NaOH ==> NaHP + H2O

moles KHP = grams/molar mass
Solve for moles.
Look at the equation; it is 1:1 so moles KHP = moles NaOH.]
The M NaOH = moles NaOH/L NaOH.