It has taken a radioactive isotope 16.2 years to decay to a mass of 2.5g. The half-life of the radioisotope is 3.24 years. What was the original mass of the isotope?
a.) 10. g
b.) 20. g
c.) 40. g
d.) 80. g

What is the typical rotational frequency frot for a molecule like n2 at room temperature (25∘c)? assume that d for this molecule is 1å=10−10m. take the total mass of an n2 molecule to be mn2=4.65×10−26kg. you will need to account for rotations around two axes (not just one) to find the correct frequency. express frot numerically in hertz, to three significant figures.