Question

Which of the following statement is not true for radioactive decay?

• A. Amount of radioactive substance remained after three half lives is $\frac{1}{8}$ th of original amount.
• B. Decay constant does not depend upon temperature.
• C. Decay constant increases with increase in temperature. $ln K=Ae^{\frac{-Ea}{RT}} \uparrow \uparrow K \uparrow$
• D. Half life is ln 2 times of $\frac{1}{\text{rate constant}}$

Answer 1

Answer: (C)

Decay constant increases with increase in temperature. $ln K=Ae^{\frac{-Ea}{RT}} \uparrow \uparrow K \uparrow$

Answer 2

Statement (1): After 3 half-lives, the remaining amount = $(\frac{1}{2})^3 = \frac{1}{8}$. (True)

Statement (2): In radioactive decay, the decay constant (λ) is a fundamental property of the nucleus and does not depend on temperature. (True)

Statement (3): The decay constant does not increase with temperature. Nuclear decay is independent of external conditions like temperature. (False)

Statement (4): The half-life $T_{1/2} = \frac{\ln{2}}{\lambda}$. (True)