1. The problem statement, all variables and given/known data I did an experiment and found the weight of CaC(2)O(4)H(2)0 to be 31.4966 subtracted by the weight of a crucible which is 31.2612. I put this for my weight of CaC204H20 (as I can't think of any other weight that it would be requested). I followed the next question calculating molecular weight. 146.112. After that I calculated the moles of CaC204H20 to be 1.6 x 10^-3 (not sure on this). I now need the moles of Ca(2+ charge). There are 27.42% Ca(2+) mass percentage of it. I don't know what to do from there. Same goes for the concentration of Ca(2+) 2. Relevant equations 3. The attempt at a solution If I had to guess, I would say the moles of Ca2+ are 0.2742 times 146.112, but I am not sure. Concentration, I have no clue. I have been looking through my online notes on this for hours now. Thanks for any help.