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In proton-proton cycle, four hydrogen at...

In proton-proton cycle, four hydrogen atoms combine to release energy

A

26.7 MeV

B

216 MeV

C

3.27 MeV

D

1 MeV

Text Solution

Verified by Experts

The correct Answer is:
A
The fusion reaction in the sum is a multi-step process in which hydrogen is burned into heium, hydrogen being the fuel and helium the ashes. The proton - proton (p, p) cycle by which this occurs is represented by the following sets of reactions :
`""_(1)^(1)H+""_(1)^(1)Hrarr""_(1)^(2)H+e^(+)+upsilon+0.42 MeV" ....(i)"`
`e^(+)+e^(-)rarr gamma+gamma+1.02MeV" ...(ii)"`
`""_(1)^(2)H+""_(1)^(1)H rarr""_(2)^(3)He+gamma+5.49MeV" ....(iii)"`
`""_(2)^(3)He+""_(2)^(3)He rarr ""_(2)^(4)He+""_(1)^(1)H+""_(1)^(1)H+"12.86 MeV ....(iv)"`
For the fouth reaction to occur, the first three reactions must occur twice, in which case two light helium nucleis. If we consider the combination `2(i)+2(ii)+2(iii)+(iv)`, the net effect is
`4""_(1)^(1)H+2e^(-)rarr""_(2)^(4)He+2upsilon+6gamma+26.7MeV`
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