If 35.50 cm3 of a NaOH solution are required for the complete neutralization of a 25.00cm3 sample of 0.200mol dm-3 H2SO4, what is the concentration of the NaOH solution?

In this question, you are given the NaOH volume but asked for concentration.

Don't forget that for every 1 mol of NaOH there will be 1 mol OH - ion, but for every 1 mol of H2SO4 there will be 2 mol of H - ion.

To neutralize you need the same amount of OH - and H+, so the equation should be:

OH - = H+

35.50cm3 * x*1 = 25cm3 * 0.2mol/dm3 * 2

x = 10/35.5 mol/dm3 = 0.2816/dm3