中五化學concentration問題 緊急!!!

Consider the chemical equation for the reaction:

2NaOH (aq) + H2SO4 (aq) → Na2SO4 (aq) + 2H2O (l)

Therefore, the molar ratio of sodium hydroxide to sulphuric acid

= 2 : 1

Number of mole of sulphuric acid

= molarity X volume

= 0.5 X 0.025

= 0.0125 mol

Therefore, number of mole of sodium hydroxide

= 2 X 0.0125 = 0.025 mol

Volume of sodium hydroxide

= no. of mole / molarity

= 0.025 / 1

= 0.025 dm^3

= 25 cm^3

So, the volume of the resulting solution

= 25 + 25 = 50 cm^3 = 0.050 dm^3

As the molar ratio of sulphuric acid to sodium sulphate = 1 : 1

So, no. of mole of sodium sulphate = 0.0125 mol

Therefore, required molarity

= no. of mole / volume

= 0.0125 / (0.050)

= 0.25 M

The answer is A.