(a) In the fusion reactions taking place within core of sun, 4 hydrogen nuclei combines to form a helium nucleus with the release of 26 MeV of energy. $4\,{}^{1}_{1}\mathrm{H}$ → $\,{}^{4}_{2}\mathrm{He} + 2e^{+}$ + 26 MeV Number of atoms in 1 kg of $\,{}^{{\underset{1}{1}}}\mathrm{H}$ , n = $\frac{1000\,\mathrm{g} \times 6 \times 10^{23}}{\text{Atomic mass}}$ = $\frac{1000\,\mathrm{g}}{1\,\mathrm{g}}$ × 6 × $10^{23}$ = 6 × $10^{26}$ atoms Energy released in the fusion of 1 kg of $\,{}^{\underset{1}{1}}$ H, $E_1$ = $\frac{6 \times 10^{26} \times 26}{4}$ MeV = 39 × $10^{26}$ MeV (b) Energy released per fission of U-235 is 200 MeV. Number of atoms in 1 kg of U-235, n = $\frac{1000\,\mathrm{g} \times 6 \times 10^{23}}{235\,\mathrm{g}}$ = 25.53 × $10^{23}$ atoms Total energy released for fission of 1 kg of uranium, $E_2$ = 25.53 × $10^{23}$ × 200 MeV = 5.1 × $10^{26}$ MeV $\frac{E_1}{E_2}$ = $\frac{39 \times 10^{26}}{5.1 \times 10^{26}}$ = 7.65 = 8 So the energy released in fusion of 1 kg of Hydrogen is nearly 8 times the energy released in fission of 1 kg of uranium-235.