What is the mass of chloride ions in 375.0 mL of solution with a magnesium chloride concentration of 0.250 M?

• A. 26.6 g
• B. 13.3 g
• C. 3.33 g
• D. 6.65 g

Answer: (B)

Verified step by step guidance

1. Determine the number of moles of magnesium chloride (MgCl₂) in the solution using the formula: \( \text{moles} = \text{molarity} \times \text{volume in liters} \). Convert 375.0 mL to liters by dividing by 1000.
2. Calculate the moles of MgCl₂ using the given molarity (0.250 M) and the volume in liters from the previous step.
3. Understand that each formula unit of MgCl₂ dissociates into one Mg²⁺ ion and two Cl⁻ ions. Therefore, the moles of Cl⁻ ions will be twice the moles of MgCl₂.
4. Calculate the moles of Cl⁻ ions by multiplying the moles of MgCl₂ by 2.
5. Convert the moles of Cl⁻ ions to mass using the molar mass of chloride ions (Cl⁻), which is approximately 35.45 g/mol. Use the formula: \( \text{mass} = \text{moles} \times \text{molar mass} \).