Final answer:
To titrate 125 mL of a 0.0100-M Ca(OH)₂ solution, 238 mL of 0.0105-M HBr solution is required.
Step-by-step explanation:
To determine the volume of 0.0105-M HBr solution required to titrate 125 mL of a 0.0100-M Ca(OH)₂ solution, we can use the balanced chemical equation and stoichiometry.
The equation shows that 1 mole of Ca(OH)₂ reacts with 2 moles of HBr. First, calculate the moles of Ca(OH)₂ in the given volume. Moles of Ca(OH)₂ = volume (L) × concentration (M) = 0.125 L × 0.0100 M = 0.00125 mol. Since the molar ratio of Ca(OH)₂ to HBr is 1:2, the moles of HBr needed is 2 times the moles of Ca(OH)₂.
Therefore, moles of HBr needed = 2 × 0.00125 mol = 0.0025 mol. Finally, calculate the volume of the 0.0105-M HBr solution needed to provide 0.0025 mol. Volume = moles (HBr) / concentration (HBr) = 0.0025 mol / 0.0105 M = 0.238 L = 238 mL.