54.5 grams of Y reacted with 13.8 g sample of X to form 68.3 g of XY.
Step-by-step explanation:
In chemical reaction the mass remains conserved until the dissipation or lost is shown. In the question it is mentioned that 13.gm of X reacts with some amount of Y to form a product XY of mass 68.3 grams.
The reaction given is addition reaction in which two elements react to for a compound.
X + Y ⇒ XY
So, in the chemical reaction value of mass is put as
13.8 + Y = 68.3
Y = 68.3-13.8
Y = 54.5 grams