Question

In a chemical reaction, the total mass of the reactants is 10.0 grams. After the reaction, the total mass of the products must be:

less than 10.0 grams.
exactly 10.0 grams.
exactly 20.0 grams.
more than 10.0 grams.

Answer 1

If you are ignoring errors and are looking at this hypothetically... the total mass of the products must be exactly 10 grams. But generally, in an experiment...you always get less mass than that of the reactants due to errors 

Answer 2

Answer: The total mass of the products will be exactly 10.0 grams.

Step-by-step explanation:

Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.

This also means that total mass on the reactant side must be equal to the total mass on the product side.

We are given:

Total mass of the reactants = 10.0 grams

Applying law of conservation of mass:

Total mass of the products = Total mass of the reactants = 10.0 grams

Hence, the total mass of the products will be exactly 10.0 grams.