Question

a student paid little attention to the size of his burner flame while heating a 0.979 gram sample of calcium oxalate monohydrate. The final mass of the cooled solid was 0.670 gram. Was the reaction product anhydrous calcium oxalate?

Answer 1

You want to convert 0.979 g CaC2O4.H2O to mass CaC2O4 an compar with 0.670g.
Convert 0.979 g CaC2O4.H2O to mols CaC2O4.H2O, then to mols CaC2O4, then to grams CaC2O4.
0.979g CaC2O4.H2O x (1 mol CaC2O4.H2O/molar mass CaC2O4.H2O) x (1 mol CaC2O4/1 mol C2O4.H2O) x (molar mass CaC2O4/1 mol CaC2O4) = ? g CaC2O4. Compare with 0.670 g.