Chapter 9, Problem 44QAP

According to the law of conservation of mass, mass cannot be gained or destroyed in a chemical reaction. Why can't you simply add the masses of two reactants to determine the total mass of product? Choose the best answer and explain.

1. One of the reactants could be present in excess, and not all of it will be used to make the product(s).

The masses of the reactants must be converted to moles first and then added.

Not all chemical reactions follow the law of conservation of mass, especially ones with mixed physical states present.

The masses of the two reactants cannot be added until they are each multiplied by their coefficient in the balanced equation.

It is only the molar masses that are conserved in chemical reactions, not the actual mass amounts given in the laboratory.