# About the q value problem in nuclear physics

1. Nov 23, 2013

### tiantsai

About the Q values , the textbook are using the Q= Δ m c^2 where (Δ m =
mass_initial - mass_final). When Q < 0 is endothermic and when Q > 0 is exothermic
nuclear process. But i use the another way round , i use the concept of
thermodynamics and physical chemistry, Q > 0 is endothermic and Q < 0 when it is
exothermic by using (Δ m = mass_final - mass_initial). This is because to let
student easily remember and not confusing (although its violate the definition of q
value). But i have make the following step when solve q value
problem.
i) Please state which side of equation. (LHS-RHS or RHS-LHS)
ii) State either is exothermic or endothermic
iii) State whether the process can occur or not.

Magnitude will be the same but the sign is difference. It just like a spectrum
concept. E(final)-E(initial)= -ive value (emission spectrum), E(initial)-E(final)=
+ive value (emission spectrum). I don't know whether i make any mistakes in my
concept or not.