Radio-Carbon Dating

NZQA 90256 2006

Cobalt 60 is a beta emitter used in medicine. It is created in a nuclear reactor, and decays with a half-life of 5.2 years. It is stored in a lead container until it is used.

1) State why the container is made of lead

2) Determine the approximate mass of the contents five years later.

Explain your answer.

In 2001, the contents of a sealed lead container were 2.0 g of radioactive Cobalt 60.

Radio-Carbon Dating

NZQA 90256 2006

Cobalt 60 is a beta emitter used in medicine. It is created in a nuclear reactor, and decays with a half-life of 5.2 years. It is stored in a lead container until it is used.

1) State why the container is made of lead

The lead stops beta particles.

or

The lead stops radioactivity escaping

or

The lead stops gamma radiation that is produced by beta decay.

Radio-Carbon Dating

NZQA 90256 2006

Cobalt 60 is a beta emitter used in medicine. It is created in a nuclear reactor, and decays with a half-life of 5.2 years. It is stored in a lead container until it is used.

2) Determine the approximate mass of the contents five years later.

Explain your answer.

In 2001, the contents of a sealed lead container were 2.0 g of radioactive Cobalt 60.

Mass of 60Co is 2 g.

Five years later the mass is still about 2 g.

When 60Co decays it will lose an electron or an particle. Whichever the new mass of the nucleus is still very close to

the mass of the old nucleus 60Co and since only half of the 60Co atoms have decayed the total mass of the radioactive 60Co will not be significantly different to the old 60Co mass.