1. The problem statement, all variables and given/known data All of the lanthanide metals (La through Lu) react with HCL to form compounds having eithe the formula MCl2, MCl3, MCl4, (where M represents the metallic element). Each metal forms a single compound. A chemist has a 0.250g sample of a lanthanide metal, and she wishes to identify the metal. She reacts the metal with excess HCl and obtains 0.427g of the product. Based on this information, identify the metal and write the chemical formula of the product. 2. Relevant equations 3. The attempt at a solution I'm not sure the below equation is correct. I originally wrote the equation without the H2, but it did not seem to be right with conservation of mass. M + HCL —> MCl2 (or MCl3, MCl4) + H2 Basically, if the H2 does belong there, then I'd just have to guess MCl2, 3, or 4, then balance the equation, then randomly guess an element right? Seems like a lot of work.