help mee If the initial sample is 275 g what mass of the ori

help mee

If the initial sample is 2.75 g, what mass of the original iridium-192 remains after 65 days? Estimate the half-life of the radioisotope. How many days would it take for three-fourths of the sample to decay?

Solution

b) k = 1/t ln(a/a-x),

k = (1/65) ln(2.75/1.443) = 0.0099,

t1/2 = 0.693/k = 0.693/0.0099 = 70 days,

c) for 3/4 decays we require 2 half lifes = 2 x70 = 140 days