25.1 grams are still present after 8.1 days. When the Gold-198 has a half-life of 2.7 days.
The act of producing radiation spontaneously is known as radioactivity. This is accomplished by an unstable atomic nucleus that wants to give up some energy in order to move to a more stable form.
The half-life of the gold =2.7 days
Sample size = 200 grams
N is the left amount after the given time =?
Constant of rate = 0.26
The rate constant is found as;
[tex]\rm \lambda = \frac{0.693}{t^{\frac{1}{2}}} \\\\ \lambda = 0.256 \ days^{-1}[/tex]
The amount after the given time;
[tex]\rm N=N_0 \times e^{-\lambda t} \\\\\ N = 200 \times e^{-0.256 \times 8.1 \ days} \\\\N=25.1 \ gm[/tex]
Hence,25.1 grams are still present after 8.1 days.
To learn more about the radioactivity, refer to the link;
https://brainly.com/question/1770619
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