1. How much energy must be supplied to break a single 6Li nucleus into separated protons and neutrons? (masses: 6Li, 6.01347; 1H, 1.00728; 1n, 1.00867 amu)

2.The half-life of 90Sr, a byproduct of nuclear testing, is 28.8 years. If 25g of 90Sr is released into the groundwater from a nuclear waste storage site, what mass of this nuclide remains after 100 years?

3.Which statements concerning chain reactions are true?

1. When there is a supercritical mass the chain reaction accelerates until an explosion occurs.
2. When there is a sub critical mass, neutrons escape from the material without causing a reaction.
3. A critical mass is the quantity of fissionable material needed to sustain a nuclear reaction with a constant rate of fission.
4. A chain reaction occurs because the fission of uranium-235 produces (on average) 2.4 neutrons.

4. 41Ca decays by electron capture. The product of this reaction undergoes positron decay. What is the product of this second decay reaction?