Write a balanced chemical equation for the aqueous reaction between barium hydroxide and hydrobromic acid. Include physical states. Question options: Ba(OH)2(aq) + 2 HBr(g) → H2O(l) + BaBr2(s) Ba(OH)2(aq) + 2 HBr(aq) → 2H2O(l) + BaBr2(aq) Ba(OH)2(s) + HBr(aq) → H2O(l) + BaBr(aq) Ba(OH)2(s) + HBr(g) → H2O(l) + BaBr(aq)
The Correct Answer and Explanation is:
Correct Answer:
Ba(OH)₂(aq) + 2 HBr(aq) → 2 H₂O(l) + BaBr₂(aq)
Explanation:
The reaction between barium hydroxide (Ba(OH)₂) and hydrobromic acid (HBr) is a typical acid–base neutralization reaction that occurs in aqueous solution.
Step-by-Step Analysis:
Nature of Reactants:
Barium hydroxide is a strong base that fully dissociates in water to produce Ba²⁺ and 2 OH⁻ ions.
Ba(OH)₂(aq) → Ba²⁺(aq) + 2 OH⁻(aq)
Hydrobromic acid is a strong acid, meaning it completely dissociates in water into H⁺ and Br⁻ ions.
HBr(aq) → H⁺(aq) + Br⁻(aq)
Reaction Mechanism:
The H⁺ ions from the acid react with the OH⁻ ions from the base to form water (H₂O):
H⁺(aq) + OH⁻(aq) → H₂O(l)
Since each molecule of Ba(OH)₂ produces 2 OH⁻, it requires 2 moles of HBr to completely neutralize it:
Ba(OH)₂(aq) + 2 HBr(aq) → 2 H₂O(l) + BaBr₂(aq)
Physical States:
Ba(OH)₂ is dissolved in water, so it is aqueous (aq).
HBr is also in aqueous form (aq).
Water formed is a liquid (l).
BaBr₂, the salt, remains dissolved in water and is aqueous (aq).
Why Other Options Are Incorrect:
Option 1: Lists HBr as a gas and BaBr₂ as a solid, which does not reflect aqueous reaction conditions.
Option 3 and 4: Use only 1 mole of HBr and form BaBr, which is not the correct stoichiometry or product (barium forms BaBr₂ with two Br⁻ ions).
Therefore, the balanced chemical equation with correct physical states is:
Ba(OH)₂(aq) + 2 HBr(aq) → 2 H₂O(l) + BaBr₂(aq).
