2.85 mol of aluminum chloride was dissolved in 584 g of water. Calculate the mass fraction of the solute in the solution.

1. First, calculate the mass of aluminum chloride. To do this, using the Periodic Table of D.I.Mendeleev, we calculate the molar mass of salt:
M (AlCl3) = M (Al) + 3 M (CL) = 26 + 3 * 35.5 = 132.5 g / mol
Aluminum chloride weight:
m (AlCl3) = 132.5 * 2.85 = 377.625 g.
2. Now we find the mass of the solution formed as a result of adding salt to water:
m (solution) = m (water) + m (AlCl3) = 584 + 377.625 = 961.625 g.
3. Calculate the mass fraction of the dissolved substance in the solution:
w = [m (AlCl3) / m (solution)] * 100 = (377.625 / 961.625) * 100 = 39.27%
Answer: the mass fraction of the solute in the solution is 39.27%