NEET Chemistry Chemical Kinetics Questions Solved


The half-life for radioactive decay of 14C is 5730 y. An archaeological artefact contained wood had only 80% of the 14C found in a living tree. Estimate the age of the sample. [Radioactive decays follow the first order kinetics] 

(A) 1657.3 y                                                

(B) 1845.4 y

(C) 1512.4 y                                                

(D) 1413.1 y

(B) t1/2=5730 y

If a is the initial 14C activity in a living tree, then

Activity in the dead wood,at = 80100 × a

The nuclear / radioactive decays follow the first order

kinetics. So, t=2.3030.693/t1/2logaatand k=0.693t1/2

Therefore, t=2.3030.693/t1/2loga80100a

                 =2.303×5730y0.693log10080

So, t=1845.4 y

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