Chemistry Question

Question

The mass of a hydrogen atom (hydrogen-1) is 1.007825 amu; that of a tritium atom (hydrogen-3) is 3.01605 amu; and that of an α particle is 4.00150 amu. How much energy in kilojoules per mole of helium-4 produced is released by the following fusion reaction:

 

hydrogen-1 + hydrogen-3 ⟶ helium-4

Answer 1

Hello, Lynny,

The difference in mass between the two hydrogen isotopes and the particle (helium) is released as energy according to E=mc^2.

I get a difference of 0.02238 amu.

1 amu = 1.60x10^-27 kg

mass lost = 3.58x10^-29 kg

c = 3.0x10⁸ m/sec

E = (3.58x10^-29 kg)*(3.0x10⁸ m/sec)²

E = 3.22x10^-12 Joules

Well, that seems dissapointing! 10^-12 Joules??

That's just for one atom each of the hydrogen isotopes. Multiply by 6.02x10²³ atoms/mole to fond the energy release from a mole each of the reactants. That's a total of 4 grams of hydrogen isotopes. Things start picking up. That's 1.94x10¹² Joules/mole.

10¹² Joules from 4 grams of reactants.

1 BTU = 252 cal = 1.055 kJ

4 grams of reactants would produce 1.84x10⁹ BTU.

Tha's equivalent to 1.78x10⁶ cubic feet of natural gas. (That's 1,780,000 ft³)

Bob