Find the mean lifetime and decay constant for 57Co. If the activity of a 57Co radiation source is now 2.00 mCi, how many 57Co nuclei does the source contain? What will be the activity after one year?

Physics Question

1. The force constant for the internuclear force in a hydrogen molecule 1H22 is kʹ = 576 N/m. A hydrogen atom has mass 1.67 x 10-27 kg. Calculate the zero-point vibrational energy for H2 (that is, the vibrational energy the molecule has in the n = 0 ground vibrational level). How does this energy compare in magnitude with the H2 bond energy of -4.48 eV?

2. The isotope 57Co decays by electron capture to 57Fe with a half- life of 272 days. The 57Fe nucleus is produced in an excited state, and it almost instantaneously emits gamma rays that we can detect.

• (a) Find the mean lifetime and decay constant for 57Co.
• (b) If the activity of a 57Co radiation source is now 2.00 mCi, how many 57Co nuclei does the source contain?
• (c) What will be the activity after one year?