Answer:
13g
Step-by-step explanation:
The law of conversation of matter tells us that in a chemical reaction, matter is never created or destroyed, it's simply converted from one form to another. So the mass of reactants should always equal the mass of the products in a chemical reaction.
Therefore, if the total mass of the products is 30g, that means that the reactants have a mass of 17g + the other reactant to = 30g.
30g - 17g = 13g