Chemistry - Chemical Kinetics Question with Solution | TestHub

The Assertion is false. Half-life is the time required for the NUMBER OF RADIOACTIVE NUCLEI (or activity) to decrease to half its initial value, not the mass number. The mass number of an isotope remains constant during radioactive decay.

The Reason is true. The half-life ($t_{1/2}$) of a radioactive isotope is a characteristic constant for that isotope and is independent of the initial amount or concentration of the isotope. It is given by $t_{1/2}=\frac{0.693}{\lambda }$, where $\lambda$ is the decay constant.

Therefore, A is false and R is true.