A 40.0g SAMPLE OF AN ELEMENT COMBINES COMPLETELY WITH ANOTHER ELEMENT TO MAKE 112.2 OF A COMPOUND. WHAT MASS OF THE SECOND ELEMENT REACTED? hOW TO i GO ABOUT SOLVING THIS PROBLEM?

Answer 1

Mass is conserved; i.e., mass of reactants must equal mass of products.
X + Y = Z
You know X is 40.0 g. You know Z is 112.2 g. So Y is ??