A 1.575 g sample of ethanedioic acid crystals, H2C2O4.nH2O, was dissolved in water and made up to 250 cm³. One mole of the acid reacts with two moles of NaOH. In a titration, 25.0 cm³ of this solution of acid reacted with exactly 15.6 cm³ of 0.160 mol dm³ NaOH. Calculate the value of n