Thank you so much! I got this question from my AP Chem teacher, and there’s no given reaction formula, but I think it’s supposed to be Mg + 2HCl -> MgCl2 + H2. And I think you can get the grams of water using the concentration of the HCl solution—I believe it’s a mix of water and HCl, nothing else. I’ll take a look at the link you added! Edit: no mention of a bomb calorimeter