The formula mass of a compound is the sum of the atomic masses of all the atoms in the compound.
* LiCl: (1 * 6.941 u) + (1 * 35.453 u) = 42.394 u
* NaCl: (1 * 22.989 u) + (1 * 35.453 u) = 58.442 u
* KCl: (1 * 39.098 u) + (1 * 35.453 u) = 74.551 u
* MgCl2: (1 * 24.305 u) + (2 * 35.453 u) = 95.211 u
Therefore, MgCl2 has the largest formula mass among the given compounds.
