`underset(Z)overset(M)()A(g)rarr underset(Z-4)overset(M-8)()B(g)+(alpha-` particles `)`
`( alpha-` particles are helium nuclei, so will form helium gas by trapping electrons )
The radioactive disintegration follows first `-` order kinetics Starting with 1 mol of A in a 1- litre closed flask at `27^(@)C` pressure developed after tw0 half- lives is approximately.