A .972g sample of a Cacl2 2H2O/K2C2O4 H2O solid salt mixture is dissolved in 150 ml of deionized water, previously adjusted to a pH that is basic . The precipitate after having been filtered and air dried has a mass of .375g. what is the percent by mass of CaCl2 2H2O

Answer 1

I think it would help you if you wrote the equation and balanced it first thing. I assume you can do that.
The ppt is CaC2O4 and it has a mass of 0.375.
Convert that to moles CaC2O4, then to moles CaCl2.2H2O(using the coefficients in the balanced equation), then to grams CaCl2.2H2O.
Finally, %CaCl2.2H2O = (mass from the above/mass sample initially)*100 = ??
mass sample initially was 0.972 g.