Reaction energy: Calculate the reaction energy (Q value) for the reaction 7Li + 1H → 4He + 4He, given the following masses: 7Li: 7.016005 u
1H: 1.007825 u
4He: 4.002603 u
(1 u = 931.5 MeV/c²)

Question

Reaction energy: Calculate the reaction energy (Q value) for the reaction 7Li + 1H → 4He + 4He, given the following masses: 7Li: 7.016005 u 1H: 1.007825 u 4He: 4.002603 u (1 u = 931.5 MeV/c²)

Quizplus · Accepted Answer

The reaction equation can be written as follows:

7Li + 1H → 2(4He)

Using the given masses,

mass of the left-hand side = (7.016005 + 1.007825) u = 8.02383 u.

mass of the right-hand side = 2(4.002603) u = 8.005206 u.

The difference between the masses is Δm = (mass of LHS – mass of RHS) = 8.02383 u – 8.005206 u = 0.018624 u.

The reaction energy (Q value) can be calculated using Einstein's famous equation E = mc², where E is the energy, m is the mass difference, and c is the speed of light.

Q = Δmc²

= (0.018624 u) x (931.5 MeV/c²)

= 17.35 MeV (rounded to two decimal places).

Therefore, the best choice is D with the explanation as provided above.

Reaction Energy: Calculate the Reaction Energy (Q Value) for the Reaction