Question

When a lithium nucleus reacts with a proton according to the reaction ⁷Li+¹H --> 2 ⁴He,

3.1x10^-29 Kg of mass is converted to energy. Calculate the energy released per mol of Li.

Answer 1

Einstein equation states E = mc^2

Here c is the speed of light = 2.9979x10⁸ m/s

m is the mass converted to energy = 3.1x10^-29 Kg

Plugging the value in the equation

E = 3.1x10^-29 Kg x (2.9979x10^8 m/s)²

2.786 x 10^-12 kg m^2 s^-2

1 joule = 1 kg m^2 s^-2

So the binging energy of Li = 2.786x10^-12 J/atom

Now convert to kJ per mole

2.786×10^−12Joules/atom × 6.02×10^23 atoms/mole×1 kJ/1000 joules = 1.677 x 10^9 KJ/mole

Energy released per mole of Li = 1.677 x 10^9 KJ