Question

at the end of a chemical reaction, what is the total mass of the reactants compared to the total mass of the products?

Answer 1

According to the law of conversation of mass, mass cannot be created nor destroyed in a chemical reaction. Therefore, the mass will not change between the reactants and the products. 

Answer 2

According to the law of conservation of mass, the total mass of the reactants is equal to the total mass of the products.
Hope this helps~