by **Guest** » Tue Aug 16, 2005 9:03 pm

The unit Bq and Ci are Bequerel and Curie, Units of radiation. They are can also used to determine the mass/quantity of radioactive substance you have.

dN/dt = (lambda)N

radioactivity=decay constant*number of undecayed atoms

a radioactivity of Bq is one decay per second. If you know the half-life the decay constant is calculated from:

t(1/2) = ln 2 / (lambda)

Then devide the Bq rating by lambda to obtain N, the number of undecayed atoms in the sample.

Devide N by Avagadro's number 6.02x10^23 to get the number of moles of substance you have, then multiply it by its molecular weight.

This will give you the mass.

Now that you know the number of grams in one unit, you can order the correct number of units.

Or alternatively, order one unit, then weigh it!

Regards,

Rob