The first nuclear reaction utilizing particle accelerators was performed by Cock
ID: 1519671 • Letter: T
Question
The first nuclear reaction utilizing particle accelerators was performed by Cockroft and Watson. Accelerated protons were used to bombard lithium nuclei, producing the reaction 1 1H + 7 3Li 4 2He + 4 2He . Since the masses of the particles involved in the reaction were well known, these results were used to obtain an early proof of the Einstein mass-energy relation. Find the Q value of the reaction. The mass of 1 1H is 1.00782 u , the mass of 7 3Li is 7.016 u , and the mass of 4 2He is 4.0026 u .
1. 17.3445 MeV
2. 20.8976 MeV
3. 10.9098 MeV
4. 12.4532 MeV
5. 172.453 MeV
6. 6.7865 MeV
Explanation / Answer
Q = mass defect*c^2
Q = (mH + mLi - 2*mHe)*c^2
Q = (1.00782 u + 7.016 u - 2*4.0026 u)*c^2
1uc^2 = 931.5 MeV
Q = (1.00782 + 7.016 - 2*4.0026 )*931.5 MeV
Q = 17.3445 MeV
Correct option is (1)
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