To determine the atomic weight of the metal in the metal chloride compound MCl3, we need some additional information. Specifically, we require the molar mass of the compound MCl3 itself.
Once we have the molar mass of MCl3, we can calculate the atomic weight of the metal by using the percentage of the metal present in the compound.
Please provide the molar mass of MCl3, and I can assist you in calculating the atomic weight of the metal.