Question

The decay constant of a radio active element, which disintegrates to $10gms$ from $20gms$ in $10$ minutes is :

• A. $0.00693mi{n}^{-1}$
• B. $6.93mi{n}^{-1}$
• C. $0.693mi{n}^{-1}$
• D. $0.0693mi{n}^{-1}$

Answer 1

The correct option is D $0.0693mi{n}^{-1}$

Disintegrates to $10$ gms from $20$ gms.

i.e. The time duration of this decay is half life.

$t_{1/2}=10min$

$=\frac{0.693}{k}min$ where k =decay constant

$\therefore k=\frac{0.693}{10}min$

$=0.0693{min}^{-1}$