The concentration of the NaOH solution is 0.3051 mol/L.
Step 1. Calculate the moles of H_2SO_4
Moles of H_2SO_4
= 20.00 mL H_2SO_4 × (0.2500 mmol H_2SO_4/1 mL H_2SO_4)
= 5.000 mmol H_2SO_4
Step 2. Calculate the moles of NaOH
Moles of NaOH = 5.000 mmol H_2SO_4× (2 mmol NaOH /1 mmol H_2SO_4)
= 10.00 mmol NaOH
Step 3. Calculate the concentration of the NaOH
c = moles/litres = 10.00 mmol/32.78 mL = 0.3051 mol/L