Question

Ddt on exposure to water decomposers half-life = 10 years how much time will it take for its decomposition to 99%

Answer 1

We know decay equation of a radio active element is given by,

ln(M/M₀) = -kt

where M = final mass

M₀ = initial mass

k = constant

t = time

Given half life of a substance is 10 years, hence,

ln(1/2) = -k x 10

=> -0.7 = -10k

=> k = 0.07

Similarly for 99% decay = 1% mass remains = final mass

=> ln(1/100) = -kt

=> -kt = -4.6

=> t = 4.6/k = 4.6/0.07 = 65.71 years

Hence it will take 65.71 years to decompose to 99% .