1. The problem statement, all variables and given/known data Consider an unknown solid containing BaCl2. 2H2O (MW = 244.26296). When the unknown is heated to 160 °C for 1 h, the water of crystallization is driven off: BaCl2.2H2O(s) ---> BaCl2(s)+ 2 H2O(g) A sample originally weighing 1.9226 g weighed 1.5647 g after heating. Calculate the weight percent of Ba (MW=137.327) in the original sample. BaCl2: MW=208.2324; H2O: MW=18.0153 2. Relevant equations 3. The attempt at a solution I think I'm missing something with the water, but I'm not sure how to work it in. I figured out mol of BaCl2*2H20 1.9226 g / 244.26296 g/mol = 7.8710 mmol Calculated moles of BaCl2 1.5647 g/208.2324 g/mol = 7.514 mmol Converted this to moles Ba 7.514 mmol * 137.327 g/mol = 1.0319026 g Divided this by original weight to obtain w/w % 1.0319 g/1.9226 g = 53.67 % This is not the right answer.