Find the Q value of the reaction `H^1+Li^7 to He^4 + He^4`. Determine whether the reaction is exothermic or endothermic? The atomic mass of `H^1, He^4` and `Li^7` are 1.007825 u, 4.002603 u and 7.016004 u respectively.

Explanation

The total mass of the initial particles
`m_i`=1.007825+7.016004=8.023829 u and the total mass of the final particles
`m_f`= 2 x 4.002603 = 8.005206 u
Difference between initial and final mass of particles
`Deltam=m_i-m_f`=8.023829-8.005206= 0.018623 u
This mass is converted into energy and the reaction is exothermic. The Q value is positive and given by
`Q=(Deltam)c^2`=0.018623 x 931.5 = 17.35 MeV