SO2+NaOH

The reaction between sulfur dioxide (SO2) and sodium hydroxide (NaOH) can occur in two main forms, depending on the conditions:

1. When sulfur dioxide is dissolved in sodium hydroxide solution:
   This reaction primarily forms sodium sulfite (Na2SO3). The balanced chemical equation for this reaction is:

   \[ SO_2 (g) + 2NaOH (aq) \rightarrow Na_2SO_3 (aq) + H_2O (l) \]

2. If excess NaOH is present:
   Sodium sulfate (Na2SO4) can be formed. This reaction occurs through the oxidation of sulfite ions. The balanced equation for this reaction is:

   \[ SO_2 (g) + 2NaOH (aq) + H_2O (l) \rightarrow Na_2SO_4 (aq) + 2H_2 (g) \]

For exams, it is important to be able to identify the products of these reactions and the stoichiometric coefficients in the balanced equations.