If 12 atoms of hydrogen enter into a chemical reaction how many atoms of hydrogen must come out of this reaction

No atoms are created or destroyed in a chemical reaction.  So if 12 go in, 12 of the same element have to come out.

hi there!

out of the two, (b) precision would be more reasonable.   however, both a and b could be pretty reasonable.

-awesomerepublic   : )

jupiter is the largest planet in our solar system, having a mass and radius that are respectively, 318 and 11.2 times that of earth. suppose that an object falls from rest near the surface of each planet and that the acceleration due to gravity remains constant during the fall. each object falls the same distance before striking the ground. determine the ratio of the time of fall on jupiter to that on earth.