Given data:
The mass of sample is m=800 g.
The halft life of sample is T=4 hrs.
The time at which mass is required is t=24 hr.
The formula to calculate the mass left in a radioactive decay is given by,
Here, m(t) is the mass at t=24 hrs.
Substitute the given values in above equation,
Thus, the mass of radioactive isotoper after 24 hrs is 12.5 gram.