Potassium-40 can decay in three modes .It can decay by `beta^(-)` - emission,`beta^(+)` -emission or electron capature. (a) Write the equation showing the end products. (b) Find the Q-value in each of the three cases. Atomic masses of `Ar_18^40`,`K_19^40`and `Ca_20^40` are 39.9624 u,39.9640 u,and 39.9626 u respectively.

Answer

`._(19)^(40)K to ._(20)^(40)Ca + e^(-) + barv, ._(19)^(40)K to ._(18)^(40)Ar + e^(+) + v, ._(19)^(40)K + e^(-) to ._(18)^(40)Ar + v`