Suppose an unknown compound XY has an X-to-Y mass ratio of 4.0. If decomposition of compound XY gives 12.0 grams of X, then how many grams of Y must form? Suppose an unknown compound XY has an X-to-Y mass ratio of 4.0. If decomposition of compound XY gives 12.0 grams of X, then how many grams of Y must form? 12.0 grams 3.0 grams 48.0 grams 4.0 grams none of the above