Final answer:
To prepare a 500 mL solution of 0.750 M MgCl2, the student needs to dissolve 35.7 grams of MgCl2 in water.
Step-by-step explanation:
The question asks how much MgCl2 (magnesium chloride) is needed to make a 0.750 M solution in a 500.0 mL volume. Molarity (M) is defined as the number of moles of solute per liter of solution. To find the mass of MgCl2 required, use the formula: mass = molarity (×) molar mass (×) volume (in liters).
The molarity is 0.750 M, the molar mass of MgCl2 is 95.2 g/mol, and the volume of the solution should be converted to liters, which is 0.5000 L (since 1 mL = 0.001 L). Using these values, the calculation will be: mass = 0.750 M × 95.2 g/mol × 0.5000 L = 35.7 g. Therefore, 35.7 grams of MgCl2 should be dissolved in water to prepare a 500 mL solution at 0.750 M concentration.