Final answer:
The volume of the solution after dissolving the sodium sulfate in water is 0.210 L.
Step-by-step explanation:
The volume of the solution formed when 4.81g of sodium sulfate, Na2SO4, is dissolved into 0.210L of water, assuming it does not change the volume significantly, remains the same as the initial volume of water. Therefore, the volume of the solution is 0.210 L, which aligns with option a. This assumption is based on the principle that the solute's volume is negligible compared to the solvent's volume, which is generally valid for dilute solutions in chemistry.