Question

A chemist wishes to make a solution using 3.61 g of CoCl₃ in which the total concentration of Cl– ions is equal to 0.333 mol/L. What must the final volume of the solution be?

Answer 1

The chemist must prepare a 196.2 mL solution to achieve the desired 0.333 mol/L concentration of chloride ions by dissolving 3.61 g of CoCl₃.

Step-by-step explanation:

To determine the final volume of the solution that would give a chloride ion concentration of 0.333 mol/L (molarity), you would follow these steps:

1. Calculate the number of moles of CoCl₃ using its molar mass.
2. Determine the total number of moles of Cl⁻ ions, since there are 3 Cl⁻ ions for each CoCl₃ formula unit.
3. Use the desire chloride ion concentration to find the final volume of the solution.

Now, let's perform the calculations:

1. Molar mass of CoCl₃ is approximately 58.93 (Co) + 3×35.45 (Cl) = 165.28 g/mol.

2. Number of moles of CoCl₃ = 3.61 g / 165.28 g/mol = 0.0218 mol.

3. Total number of moles of Cl⁻ = 0.0218 mol CoCl₃ × 3 mol Cl⁻/mol CoCl₃ = 0.0654 mol Cl⁻.

4. To find the volume: Volume = number of moles of Cl⁻ / molarity of Cl⁻ = 0.0654 mol / 0.333 mol/L = 0.1962 L or 196.2 mL.

Therefore, the chemist must prepare a 196.2 mL solution to achieve the desired chloride ion concentration.