Question

Iodine-131 has a half-life of 8 days. How many days will it take before 32mg of Iodine-131 has decayed to 1mg?

Answer 1

Answer:40 days

- K = [ ln ( 1/2 ) ] / [ t 1/2 ]

- K = [ln ( 1/2 ) ] / 8 = - 0.08664 ( days )^-1

ln C/ C0 = ( - K ) ( t )

C=1mg and C0= 32mg

t = [ ln (1/32 )] / [ - 0.08664 ] = 40 days