Question

In the proton-proton cycle, the fusion reactions involve the conversion of hydrogen nuclei. The energy output in each reaction is as follows:

a) (p + p → ²H + e⁺ + nuₑ), Energy Released: 0.42 MeV
b) (p + ²H → ³He + γ), Energy Released: 5.49 MeV
c) (³He + ³He → ⁴He + ¹H + ¹H), Energy Released: 12.86 MeV
d)none of the above

Answer 1

The proton-proton cycle describes how stars like the Sun fuse hydrogen into helium to produce energy. The total energy released in this process is 26.7 MeV for each complete cycle.

Step-by-step explanation:

The proton-proton cycle is a series of fusion reactions through which stars like the Sun convert hydrogen into helium, releasing energy. The following are the stated energy outputs for each step of the cycle:

(p + p → ²H + e⁺ + νₑ), Energy Released: 0.42 MeV

(p + ²H → ³He + γ), Energy Released: 5.49 MeV

(³He + ³He → ⁴He + ¹H + ¹H), Energy Released: 12.86 MeV

Since the first two reactions must occur twice for the third reaction to occur, the total energy released during a complete proton-proton cycle is 26.7 MeV, accounting for the positron annihilations that release additional energy. One proton-proton cycle results in the fusion of four protons into one helium-4 nucleus, two positrons, two electron neutrinos, and six gamma photons.