Ten grams of 57 Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly.

Question

Philoid · Accepted Answer

A neutron is converted to a proton with creation of an electron and an antineutrino during beta-decay. The rest mass of antineutrino is approximately zero (though unknown in physics till now) while the rest mass of an electron is kg. Thus the mass of a beta particle is much less when compared to the mass of Co atom. Hence even after 540 days in a container, the weight of the material will be approximately equal to 10g.

Ten grams of 57Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly.

Ten grams of ⁵⁷Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly.