Question

The combustion of a single molecule of methane produces about 10 ev of energy. a methane molecule has a mass of 16 amu. the fission of a uranium-235 atom produces about 189 mev of energy. based on these numbers, about what mass of methane will produce as much energy as a single gram of uranium-235?

Answer 1

If one molecule of methane produces 10eV then we need:
$n=\frac{189MeV}{10eV}$,
molecules of methane to get 189MeV.
$n=\frac{189MeV}{10eV}=\frac{189}{10}\cdot 10^6=18900000$
To get the mass we simply multiply this number by the mass of one molecule of methane.
$m=16\cdot18900000=302400000amu$
One atomic mass unit is:
$amu=1.66053904\cdot 10^{-24} g$
There we would need:
$m=302400000\cdot1.66053904\cdot 10^{-24}=5.0214701\cdot10^{-16} g$
grams of methane.