If there are 2 grams of product produced by the chemical reaction, how many grams of reactant were consumed? a) 0 grams b) 1 gram c) 2 grams d) 4 grams

2grams. Due to the las of consevation of mass.  These implies that mass quantity can not change,

The amount of reactant consumed is 2 grams

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:

Mass of the product = 2 g

Applying law of conservation of mass, we get:

Mass of reactant = Mass of product = 2 g

Hence, the amount of reactant consumed is 2 grams

i believe the answer is three water molecules