Which one of the following represents the net ionic equation for the reaction of HBr with Ca(OH)_2?

• A. Br^- (aq) + Ca^{2+} (aq) → CaBr_2 (aq)
• B. HBr (aq) + Ca(OH)_2 (aq) → CaBr_2 (aq) + 2H_2O (l)
• C. 2H^+ (aq) + 2Br^- (aq) + Ca^{2+} (aq) + 2OH^- (aq) → CaBr_2 (aq) + 2H_2O (l)
• D. 2H^+ (aq) + 2OH^- (aq) → 2H_2O (l)

Answer: (D)

Verified step by step guidance

1. Identify the reactants and products in the given reaction: HBr (a strong acid) reacts with Ca(OH)_2 (a strong base) to form CaBr_2 (a salt) and water.
2. Write the full balanced molecular equation: \(\mathrm{2\ HBr\ (aq) + Ca(OH)_2\ (aq) \rightarrow CaBr_2\ (aq) + 2\ H_2O\ (l)}\).
3. Dissociate all strong electrolytes into their ions to write the complete ionic equation: \(\mathrm{2\ H^+\ (aq) + 2\ Br^-\ (aq) + Ca^{2+}\ (aq) + 2\ OH^-\ (aq) \rightarrow Ca^{2+}\ (aq) + 2\ Br^-\ (aq) + 2\ H_2O\ (l)}\).
4. Cancel the spectator ions (ions that appear unchanged on both sides of the equation). Here, \(\mathrm{Ca^{2+}}\) and \(\mathrm{Br^-}\) ions are spectators and can be removed.
5. Write the net ionic equation with only the species that undergo change: \(\mathrm{2\ H^+\ (aq) + 2\ OH^-\ (aq) \rightarrow 2\ H_2O\ (l)}\).