Answer:then the number of grams of Y that must form is 3
Step-by-step explanation:
Suppose an unknown compound XY has an X-to-Y mass ratio of 4.0, it means that
X/Y = 4
Crossmultiplying,
X = 4Y
If decomposition of compound XY gives 12.0 grams of X, then the number of grams of Y that must form would be
X = 4Y
Substituting X = 12 into the equation, it becomes
12 = 4Y
Y = 12/4 = 3 grams