The mass of cobalt 60 in a sample is found to have decreased from 24 g to 1.5 g in a period of 21.08 years. What is the half life of cobalt 60?

Iam in desperate need of with this !

At a certain temperature the rate of this reaction is first order in hi with a rate constant of : 0.0632s2hig=h2g+i2g suppose a vessel contains hi at a concentration of 1.28m . calculate how long it takes for the concentration of hi to decrease to 17.0% of its initial value. you may assume no other reaction is important. round your answer to 2 significant digits.

What kind of intermolecular forces act between a hydrogen fluoride molecule and a hydrogen peroxide molecule? note: if there is more than one type of intermolecular force that acts, be sure to list them all, with a comma between the name of each force.