In a chemical reaction, the total mass of the reactants is 10.0 grams. after the reaction, the total mass of the products must be:

10.0 grams.

Explanation:

After the reaction, the total mass should be the same, because of the law of conservation of the mass, which says that mass is neither created or destroyed, in a isolated system. So, basically the chemical reaction doesn't change the amount of matter, but its nature.

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.