2NaOH + H2SO4 -> 2H2O + Na2SO4. moles = concentration x volume. #moles NaOH = 2M x (25/1000)dm3 = 0.05 mol. The reaction equations shows the ratio of alkali to acid is 2:1. The number of moles of H2SO4 required for neutralisation is half of the number of moles of NaOH. #mole H2SO4 = 0.05/2 = 0.025 mol. volume of H2SO4 = moles / concentration = 0.025/1.25 = 0.02 dm3.