Chemical Kinetics

The half­-life of a radioisotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is

  1. 1.042 g
  2. 2.084 g
  3. 3.125 g
  4. 4.167 g

Answer

t1/2 = 4 hours

n = T/t1/2 = 24/4 = 6

N = No(1/2)n = 200(1/2)6 = 3.125 gm

The correct option is C.