How many grams Cuo would 1.00g paris green give?of As2O3?

Question

how many grams Cuo would 1.00g paris green give?of As2O3?

Paris green?

Answer 1

Paris green is copper acetoarsenite: Cu(C2H3O2)2·3Cu(AsO2)2, a pigment no longer in use (due to its toxicity).

If we assume that all of the copper will end up as CuO, we can see from the formula that there are more moles of O than there are of Cu (even if we subtract 3 O atoms for the As2O3), so we will be limited by the amount of Cu in the compound.  The molar mass of the compound is 1013.80 g/mol.  1 gram is thus .986 mmol (9.86*10^-4 mol) of paris green.  We have 4 atoms of copper for every molecule of paris green, so we will have 4 times this many moles of CuO: 3.95mmol.  Multiply this by the molar mass of CuO (79.55g/mol, be sure to use the right units, as I gave some in mmol instead) to get the mass of CuO: 0.314g.

We do the same for As2O3: we have already checked, and there is more than enough oxygen to form all possible CuO and As2O3, so As will be the limiting atom.  We have 2 atoms of As for each molecule of paris green, so we will have 1.97mmol of As2O3.  Multiply this by the molar mass of As2O3 (197.84g/mol) to get the other answer: 0.390g of As2O3.