Question

Part A

Part complete

Choose the missing nucleus in the following reaction: 23292U??+42He+energy.

22890Th

22888Ra

22690Th

22688Ra

SubmitPrevious Answers

Correct

Part B

Calculate how much energy is released.

Express your answer using three significant figures and include the appropriate units.

Q =

7.547.54 MeVMeV

Answer 1

Using conservation of Atomic number and Atomic weight on both sides

Suppose unknown element has Z = 92 - 2 = 90

A = 232 - 4 = 228, So

²³²U₉₂ ---> ²²⁸Th₉₀ + ⁴He₂ + energy

Unknown nucleus is  ²²⁸Th₉₀

Part B.

Energy released will be given by:

Q = dm*c^2

dm = change in mass = Mass of U - Mass of Th - Mass of He

Mass of 232 U = 232.037156 amu

Mass of 228 Th = 228.028741 amu

Mass of 4 He = 4.002603 amu

dm = 232.037156 - 228.028741 - 4.002603 = 0.005812 amu

1 amu = 931.5 MeV/c^2

So

Q = dm*c^2

Q = (0.005812*931.5 MeV/c^2)*(c^2)

Q = 5.41 MeV

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