Calculate the Molarity of a Calcium Carbonate Standard Solution

To calculate the molarity of a calcium carbonate (CaCO₃) solution, we need to follow a few steps:

1. Determine the molar mass of calcium carbonate: The molar mass is calculated by adding the atomic masses of calcium (Ca), carbon (C), and oxygen (O). The atomic masses are approximately:
• Calcium (Ca): 40.08 g/mol
• Carbon (C): 12.01 g/mol
• Oxygen (O): 16.00 g/mol (there are three oxygen atoms)
2. Adding these together, we get:

Molar mass of CaCO₃ = 40.08 + 12.01 + (3 × 16.00) = 100.09 g/mol

3. Calculate the number of moles of calcium carbonate: We have 0.2430 grams of CaCO₃. Using the formula:

Number of moles = Mass (g) / Molar mass (g/mol)

Number of moles = 0.2430 g / 100.09 g/mol ≈ 0.00243 moles

4. Determine the total volume of the solution in liters: The solution volume is given as 250.0 mL. To convert mL to L:

Volume (L) = Volume (mL) / 1000 = 250.0 mL / 1000 = 0.2500 L

5. Calculate the molarity (M): Molarity is defined as the number of moles of solute divided by the volume of the solution in liters:

Molarity (M) = Number of moles / Volume (L)

Molarity (M) = 0.00243 moles / 0.2500 L = 0.00972 M

Therefore, the molarity of the calcium carbonate standard solution is 0.0097 M when expressed to four decimal places.