When vinegar was combined with baking soda and sealed in a plastic quart bag, the total mass of the products was 70 g. What was the total mass of the vinegar and baking soda before the reaction took place?

A. 0 g

B. 35 g

C. 70 g

D. 140 g

The answer is C) 70.

Because the reaction was sealed in a plastic bag, none of the vinegar or baking soda was able to escape as a gas. The law of conservation of mass states that mass cannot be created or destroyed, therefore the same amount must have been present before the reaction took place, and there was 70g of vinegar and baking soda.