Answer:
[tex]9.53*10^{17}[/tex] atoms of 40K
Explanation:
You can use the molecular mass and the Avogadro´s number, in the following formula:
[tex]N_{40K=\frac{m_{KCl}}{M_{MKCl}}}*N_{Avogadro}*(IA_{40k})[/tex]
where [tex]m_{KCl}[/tex] is the sample mass, [tex]M_{KCl}[/tex] is the molecular mass of the KCl and IA(40K) is the isotopic abundance of 40K.
Now replacing the values, you can find:
[tex]N_{40K}=\frac{1g}{74.5513\frac{g}{mol}}*6.022*10^{23}mol^{-1} *0.000118[/tex]
[tex]N_{40K}=9.53*10^{17} atoms[/tex]
