What Is The Mechanism Of The Reaction Between Sodium Metabisulfite And Water?

The reaction between sodium metabisulfite and water involves the hydrolysis of the compound, which is a type of chemical reaction where water molecules break down the compound into its constituent ions or molecules. Specifically, in this reaction, water reacts with the sodium metabisulfite (Na2S2O5) to form sodium bisulfite (NaHSO3) and sulfur dioxide (SO2). The overall reaction can be represented as follows:

Na2S2O5 + H2O → 2 NaHSO3 + SO2

This reaction occurs because the water molecule acts as a nucleophile, attacking one of the sulfur atoms in the metabisulfite ion (S2O5^2-) and cleaving the S-S bond, resulting in the formation of two sulfite ions (HSO3^-). The sodium ions (Na+) in the original compound remain unchanged and are simply solvated by the water molecules.

Overall, this reaction is important in many industrial processes, including as a means of generating sulfur dioxide gas for various applications.