Question 192: Atoms & Nuclei

Question

The half-life of ${}^{198}Au$ is 3 days. If atomic weight of ${}^{198}Au$ is 198 g/mol then the activity of 2 mg of ${}^{198}Au$ is [in disintegration/second] :

Accepted Answer

A = $\lambda$N
$\lambda  = {{\ln 2} \over {{t_{1/2}}}} = {{\ln 2} \over {3 	imes 24 	imes 60 	imes 60}}$sec
$-$1
= 2.67 $	imes$ 10
$-$6
sec
$-$1
N = Number of atoms in 2 mg Au
$ = {{2 	imes {{10}^{ - 3}}} \over {198}} 	imes 6 	imes {10^{23}}$ = 6.06 $	imes$ 10
15
$A = \lambda N = 1.618 	imes {10^{13}} = 16.18 	imes {10^{12}}$ dps

Answer

2.67 $	imes$ 10
12

Answer

6.06 $	imes$ 10
18

Answer

32.36 $	imes$ 10
12

Answer

16.18 $	imes$ 10
12

Atoms & Nuclei

The half-life of {}^{198}Au is 3 days. If atomic weight of {}^{198}Au is 198 g/mol then the activity of 2 mg of {}^{198}Au is [in disintegration/second] :

Choose the correct answer: