Posted by: ginnynorman | May 23, 2010

Balancing Nuclear Rxns

Here is a worksheet with full solutions that will help you revise and practice balancing equations, enjoy!


  1. I dislike the question on the mass of a radioisotope which remains after a decay time. With very few exceptions the change in mass which occurs when a sample undergoes beta decay is very small.

    The biggest change I imagine which would occur would be if I was to have a gram sized carrier free solid sample of I-131. As it decays it would form xenon and the mass of the solid would change.

    Alpha decay is a different matter as the helium formed has some mass. If I was to seal up lots of Pu-238 powder in a vacuum then after a few years helium would be detected in the container.

    A funny one which relates to a change in P is pure tritium gas, if you were to seal up a cylinder of pure tritium gas (10 bar) then after about ten years P would equal 20 bar. This is becuase hydrogen is a diatomic gas while helium is a monoatomic gas.

    It is better to consider the change in radioactivity level than the mass

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