Question

Xenon-133 is used to test lung function; it decays by emitting a beta particle.....

1.)Write an equation for the beta decay of Xe-133.

2.)If the half-life of Xe-133 is 5.2 h, how much of a 10.-mCi sample is still active after 15.4 h?

Write the balanced nuclear equation for each of the following:

1.) Actinum-225 decays to give francium-221.

2.) Bismuth-211 emits an alpha particle.

3.) A radioisotope emits a positron to form germanium-74.

4.) An atom of germanium-69 emits a positron.

Answer 1

1. In beta decay, an electron with a charge of -1 and mass of 0 is emitted. Hence Xe decays to an element whose atomic number is 1 greater than the atomic number of Xe. The total atomic numbers on both sides of the reaction should be equal and the total mass number on both sides should be equal. Xe decays to cesium.

2. The formula is A= A(ini) *(1/2)^(t/h) , where A is concentration after time t, A(ini) is initial concentration, h is half life.

A = 10*(1/2)^(15.4/5.2)

A = 10*(1/2)^(2.961) = 10*0.1284 = 1.284 mCi

1.284 mCi of sample is still left.

3.