Question

Calculate the amount of energy in joules that would be produced if 2.50 x 10^-3 kilogram of matter was entirely converted to energy.

Answer 1

To solve the problem, we can use the Einstein's famous equivalence between energy and mass:
$E=mc^2$
where 
E is the energy
m is the mass
c is the speed of light

In this problem, the mass of the substance is $m=2.50 \cdot 10^{-3} kg$, so if all this mass would be converted in energy, we would have an energy of
$E=mc^2=(2.50 \cdot 10^{-3} kg)(3 \cdot 10^8 m/s)^2=2.25 \cdot 10^{14} J$