An unknown metal chloride has the formula MClx. The addition of 28.9 mL of 0.432 M aqueous lead (II) nitrate to 26.7 mL of 0.311 M aqueous MClx causes all the lead ions and chloride ions present in solution to precipitate out as lead (II) chloride (i.e., a stoichiometric amount of lead nitrate is used) which of the following substances listed below could have been the metal chloride?
MgCl2, NaCl, AlCl3.