Question

A sample of rock is found to contain 200 grams of a parent isotope.how many grams of the parent isotope will remain after one half life

Answer 1

Answer:

50

Explanation:

Answer 2

Answer: 100 grams of the parent isotope will remain after one half life.

Explanation:

Mass of the isotope present at initial stage = $N_o=200 g$

The mass of the parent isotope left after the time ,t=N

Time taken by the samle ,t = $t_{\frac{1}{2}}$

The half life of the sample :$t_{\frac{1}{2}}$

$N=N_o\times e^{-\lambda t}$

$\lambda =\frac{0.693}{t_{\frac{1}{2}}}$

$\ln[N]=ln[N^o]-\frac{0.693}{t_{\frac{1}{2}}}\times t_{\frac{1}{2}}$

$2=\frac{[N_o]}{[N]}$

$[N]=\frac{N_o}{2}=\frac{200 g}{2}=100 g$

100 grams of the parent isotope will remain after one half life.