How many grams of Ca(OH)_2 are required to prepare 100 mL of a 0.250 M solution?

• A. 0.46 g
• B. 0.25 g
• C. 0.74 g
• D. 1.85 g

Answer: (D)

Verified step by step guidance

1. Identify the given information: volume of solution (100 mL) and molarity (0.250 M). Convert the volume from milliliters to liters because molarity is expressed in moles per liter. Use the conversion: \$100\ \text{mL} = 0.100\ \text{L}$.
2. Use the molarity definition to find the number of moles of Ca(OH)\(_2\) needed: \(\text{moles} = M \times V = 0.250\ \text{mol/L} \times 0.100\ \text{L}\).
3. Calculate the molar mass of Ca(OH)\(_2\) by summing the atomic masses: Calcium (Ca) = 40.08 g/mol, Oxygen (O) = 16.00 g/mol, Hydrogen (H) = 1.008 g/mol. So, \(\text{molar mass} = 40.08 + 2 \times (16.00 + 1.008)\) g/mol.
4. Convert moles of Ca(OH)\(_2\) to grams using the molar mass: \(\text{mass} = \text{moles} \times \text{molar mass}\).
5. The resulting mass is the amount of Ca(OH)\(_2\) required to prepare 100 mL of a 0.250 M solution.