A 0.2861 gram sample of an unknow acid (HX) required 32.63 mL of 0.1045 m NAOH for neutralization to a thenolphthalein end point. what is the molar mass of the acid?

Find the moles of OH- = moles NaOH

moles OH- = (liters)(molar concentration)
moles of HX = moles of OH-
molar mass = (grams of HX) / moles HX