Acertain radioactive element has a half-life of one hour. if you start with 40.0 grams of the element at noon, how much of the radioactive element will be left at 2 p. m.?

a.) 20.0 grams
b.) 10.0 grams
c.) 5.0 grams
d.) 0.0 grams

How is electrolysis most commonly used to produce an energy source? a - splitting water molecules produces oxygen, which organisms breathe to fuel their bodies. b - splitting water molecules produces hydrogen gas, which is used to power machines through hydrogen fuel cells. c - splitting carbon dioxide molecules produces coal, a form of carbon that can be burned to produce heat. d - splitting carbon dioxide molecules produces natural gas, which can be burned to generate electricity in power plants.