How do you get the energy of products in nuclear reaction?

[zutto]

The radionuclide X has a half life of 2.58hours and is produced in a cyclotron at a constant rate by bombarding a Y target with 2.10 MeV deuterons. The target contains only the stable isoptope Y and the reaction that produces X is

Y + deuteron -> X + proton

show that energy is released in this reaction,
and hence calculate the energy of the products in the above reaction.

(atomic mass of Y = 54.938047u, X = 55.938906u, deuteron = 2.014102u, proton = 1.007825u)

ANS: energy of products = 1.145 x 10^-12 J

how do you get energy of products? i don't understand.

why can't i get the answer by taking (mass of X + mass of proton)(u)c^2?

thanks in advance! :)

 

[Simon Bridge]

Welcome to PF:
You have a stationary target of Y with a moving d at the start, and a recoiled X with a moving p after.

You are not asked to work out how the energy of the products is distributed.
So you do 1. by comparing the masses before and after (remember the 2MeV incoming).

You do 2 by conservation of total energy.

why can't i get the answer by taking (mass of X + mass of proton)(u)c^2?

because that would be the rest-mass energy of the products ... you need their kinetic energies too.