$A$ radioactive isotope having a half-life period of $3 \ days$ was received after $12 \ days$. If $3 \ g$ of the isotope is left in the container,what would be the initial mass of the isotope?.......... $g$

The half-life of $C^{14}$ is $5760 \ years$. For a $200 \ mg$ sample of $C^{14}$,the time taken to change to $25 \ mg$ is (in $years$)

The half-life of the radio element $_{83}Bi^{210}$ is $5 \ days$. Starting with $20 \ g$ of this isotope,the amount remaining after $15 \ days$ is ......... $g$. (in $g$)

$A$ radioactive substance has a constant activity of $2000$ disintegrations/minute. The material is separated into two fractions,one of which has an initial activity of $1000$ disintegrations per minute while the other fraction decays with $t_{1/2} = 24 \ h$. The total activity in both samples after $48 \ h$ of separation is

The half-life period of a radioactive element is $140$ days. After $560$ days,one gram of the element will reduce to

What is the value of the decay constant of a compound having a half-life time $T_{1/2} = 2.95 \text{ days}$?