Answer: The total mass of reactants is 70 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.
The chemical equation for the reaction of vinegar (acetic acid) and baking soda (sodium bicarbonate) follows:

We are given:
Total mass of products = 70 grams
Applying law of conservation of mass, we get:
Total mass of reactants = Total mass of products
Total mass of reactants = 70 g
Hence, the total mass of reactants is 70 grams.