Is this the right answer???

If the mass of the products measured 120g what would the mass of the reactants a. 30g b. 60g c. 120g d. 240g

What is conserved in the reaction shown below? h2(g) + cl2 (g) --> 2hcl(g)a. mass onlyb. mass and moles onlyc. mass, moles, and molecules onlyd. mass, moles, molecules, and volume

How do you know when a chemical reaction has occurred