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Caesium-137 is a radioactive isotope of the alkali metal caesium - Leaving Cert Chemistry - Question c - 2013
Question c
Caesium-137 is a radioactive isotope of the alkali metal caesium. Caesium-137 was released into the atmosphere when Japanese nuclear reactors were damaged by a tsuna... show full transcript
Worked Solution & Example Answer:Caesium-137 is a radioactive isotope of the alkali metal caesium - Leaving Cert Chemistry - Question c - 2013
Step 1
Step 2
Give two differences between chemical reactions and nuclear reactions.
Answer
- Chemical reactions involve the rearrangement of electrons and do not result in a change to the nuclei of the reacting atoms, whereas nuclear reactions involve changes to the nucleus itself and can result in the formation of new elements.
- In chemical reactions, mass conventions are preserved with respect to the reactants and products, while in nuclear reactions, mass can be converted into energy according to Einstein's equation, .
Step 3
Give two properties of beta-particles.
Answer
- Beta-particles are negatively charged particles (electrons) that are emitted during beta decay and travel at high speeds—approaching the speed of light.
- They are moderately penetrating, able to pass through paper but stopped by materials like aluminum or plastic.
Step 4
What fraction of this mass remained as caesium-137 after 90 days?
Answer
The half-life of caesium-137 is 30 days. After 90 days, which is 3 half-lives (90 / 30 = 3), the fraction of the original mass remaining can be calculated as follows:
ext{Remaining mass} = rac{1}{2^n} For 3 half-lives:
ext{Remaining mass} = rac{1}{2^3} = rac{1}{8} ext{ or } 12.5\% Thus, the fraction remaining after 90 days is one-eighth or 12.5%.