Final answer:
The mass % of acetonitrile in a 2.17 M solution with a density of 0.810 g/mL is approximately 11.00%, which is determined by multiplying the molarity of the solution by the molar mass of acetonitrile and then dividing by the mass of the solution per liter.
Step-by-step explanation:
To calculate the mass % of acetonitrile in a 2.17 M solution with a density of 0.810 g/mL, we must first determine the total mass of acetonitrile in a given volume of the solution and then find the total mass of the solution.
Given that the molar mass (MM) of acetonitrile (CH3CN) is 41.05 g/mol, we can calculate the mass of acetonitrile per liter of solution by multiplying the molarity of the solution by the molar mass:
Mass of acetonitrile per liter = 2.17 mol/L × 41.05 g/mol = 89.08 g/L
To find the mass of the solution, we use the density:
Mass of solution per liter = 0.810 g/mL × 1000 mL/L = 810 g/L
The mass percentage is then calculated as:
Mass % of acetonitrile = (Mass of acetonitrile per liter / Mass of solution per liter) × 100
Mass % of acetonitrile = (89.08 g/L / 810 g/L) × 100 ≈ 11.00%
Therefore, the mass % of acetonitrile in the solution is approximately 11.00%.