Addition of sulfurous acid (a weak acid) to barium hydroxide (a strong base) results in the formatio — Acids and Bases Chemistry Question

STEPS:

1. Classify the chemical nature of the reactants:
* Sulfurous acid ($\text{H}_2\text{SO}_3$) is explicitly identified as a weak acid. In aqueous solution, weak acids are weak electrolytes and do not extensively ionize; therefore, they must be written in their intact molecular form, $\text{H}_2\text{SO}_3(aq)$, in both complete and net ionic equations.
* Barium hydroxide ($\text{Ba(OH)}_2$) is a soluble strong base. Strong bases are strong electrolytes that dissociate completely in aqueous solution into their constituent ions: $\text{Ba}^{2+}(aq)$ and $\text{OH}^-(aq)$.
2. Identify the products of the neutralization reaction:
* The reaction between $\text{H}_2\text{SO}_3$ and $\text{Ba(OH)}_2$ is an acid-base neutralization that forms water ($\text{H}_2\text{O}(l)$) and the salt barium sulfite ($\text{BaSO}_3$).
* The prompt states that a precipitate forms. Therefore, barium sulfite must be represented as an insoluble solid: $\text{BaSO}_3(s)$.
3. Write the complete molecular equation:
$$\text{H}_2\text{SO}_3(aq) + \text{Ba(OH)}_2(aq) \rightarrow \text{BaSO}_3(s) + 2\text{ H}_2\text{O}(l)$$
4. Write the complete ionic equation:
Dissociate only the strong electrolyte ($\text{Ba(OH)}_2$) while keeping the weak acid, solid precipitate, and liquid water intact:
$$\text{H}_2\text{SO}_3(aq) + \text{Ba}^{2+}(aq) + 2\text{ OH}^-(aq) \rightarrow \text{BaSO}_3(s) + 2\text{ H}_2\text{O}(l)$$
5. Identify and eliminate spectator ions to find the net ionic equation:
Spectator ions are species that appear in the exact same form on both the reactant and product sides of the equation. In this reaction, every single ion undergoes a chemical change (forming either insoluble solid $\text{BaSO}_3$ or molecular liquid $\text{H}_2\text{O}$). Since there are no spectator ions, the complete ionic equation is also the net ionic equation. This matches Option B.

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WHY_OTHERS_WRONG:

• A is incorrect: This is the net ionic equation for a standard neutralization reaction between a strong acid (which fully dissociates into free $\text{H}^+$ ions) and a strong base when no precipitate is formed. It fails to account for the weak acid reactants and completely ignores the formation of the solid precipitate.
• C is incorrect: This equation incorrectly represents sulfurous acid ($\text{H}_2\text{SO}_3$) as being completely dissociated into free $\text{H}^+$ and $\text{SO}_3^{2-}$ ions. Since it is a weak acid, it must be kept intact as $\text{H}_2\text{SO}_3(aq)$ on the reactant side.
• D is incorrect: This equation fails to show the formation of a precipitate. It incorrectly represents barium and sulfite as separated aqueous ions on the product side, contradicting the observation that a precipitate of $\text{BaSO}_3(s)$ forms.
• E is incorrect: This represents the balanced molecular equation, not the net ionic equation. Barium hydroxide is a strong electrolyte and must be split into its dissociated ions ($\text{Ba}^{2+}$ and $\text{OH}^-$) in any ionic representation.