Question

one kilogram of uranium can produce as much energy as 16,000 kilograms of coal. why is the energy output for uranium so much greater than the energy output for coal?
uranium undergoes many more steps of purification than coal does before it is used in reactions.
uranium is a highly reactive metal that reacts violently with oxygen during combustion.
uranium undergoes fission, and nuclear reactions give off more energy than chemical reactions.
uranium is extremely radioactive and gives off higher electromagnetic radiation than burning coal.

Explanation:

Uranium undergoes nuclear fission, a nuclear reaction. Coal combustion is a chemical reaction. Nuclear reactions release much more energy than chemical reactions due to the conversion of a small amount of mass into a large amount of energy (as per Einstein's \(E = mc^{2}\)). Purification steps don't explain the energy difference. Uranium is not burned in the traditional combustion (with oxygen) sense like coal. While uranium is radioactive, the key is the type of reaction (nuclear vs chemical) for energy output difference.

Answer:

Uranium undergoes fission, and nuclear reactions give off more energy than chemical reactions.