What mass of Ca(OH)_2 is required to react completely with a 25.00 mL sample of 0.1234 M HCl(aq)?

• A. 0.215 g
• B. 0.344 g
• C. 0.0860 g
• D. 0.172 g

Answer: (D)

Verified step by step guidance

1. Write the balanced chemical equation for the reaction between calcium hydroxide and hydrochloric acid: \(\mathrm{Ca(OH)_2 + 2HCl \rightarrow CaCl_2 + 2H_2O}\).
2. Identify the molarity and volume of HCl given: Molarity \(M = 0.1234\, \mathrm{mol/L}\) and volume \(V = 25.00\, \mathrm{mL} = 0.02500\, \mathrm{L}\).
3. Calculate the moles of HCl using the formula: \(\mathrm{moles\ HCl = M \times V = 0.1234 \times 0.02500}\).
4. Use the stoichiometric ratio from the balanced equation to find moles of \(\mathrm{Ca(OH)_2}\) needed: \(\mathrm{moles\ Ca(OH)_2 = \frac{1}{2} \times moles\ HCl}\).
5. Calculate the mass of \(\mathrm{Ca(OH)_2}\) required using its molar mass (approximately 74.09 g/mol): \(\mathrm{mass = moles \times molar\ mass}\).