Help for the Equilibrium Constant from a Titration

So this is just a hypothetical problem but ultimately I have to find the equilibrium constant for this equation using the process of titration for 2NaOH + H2SO4 = NaSO4 + 2H2O. Say we have sulfuric acid of unknown concentration with 25mL of it in a beaker. We also have the titrant NaOH with a concentration of .12 Molars. Once the titration process has ended and the final solution is neutral, I ended up using 18.3mL of NaOH solution. After some calculations, I find out that there is .002196 moles of NaOH. Using the 2:1 ratio is the equation, that means that there must be .001098 moles of H2SO4. After further calculations, I find that the concentration of H2SO4 is .04392 M. From here I get stuck on what to do next. To find the equilibrium constant, I know I must know the concentrations of the reactants and products. I know the reactants' concentrations and the H20 product is not taken into account since it is a liquid. Therefore, I still have to find the concentration of Na2SO4. To find its concentration, I must know it's volume it takes up and the amount of it in moles. I think, correct me if i'm wrong, that the amount of Na2SO4 is .001098 moles. But I still can't find how to find its volume. Any help with this problem would be greatly appriciated. This is just a practice problem that I assembled to practice titration for an upcoming competition so not everything may be what it would be if I actually performed this experiment.