Radioactivity : mass of sample

In summary, the conversation discusses finding the number of radioactive atoms and the approximate mass of a sample containing 6GBq of 99mTc. The solution involves calculating the decay constant (λ) using the given half life of 6 hours, and then using it to find the number of nuclei (N). The approximate mass of the sample is then determined by multiplying the number of nuclei by the mass number and dividing by Avogadro's number. The resulting mass is 8.18 × 10^-7 kg.
  • #1
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Homework Statement



How many radioactive atoms are present in a sample of 6GBq of 99mTc and what is the approximate mass of the sample?

Homework Equations



A= λN
half life = ln2/λ
mass = (no.nuclei * mass number)/avorgado number
avogado = 6.023×10^23
half life = 6 hours

The Attempt at a Solution



worked out λ using the above half life (6 hours) and then N (no. nuclei). My problem is that we was not given the half life to beign with. Is there any other way of working it out without the half life ?
 
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  • #2
N = 6GBq / λ λ= ln2 / half life λ = 0.693 / 6 λ = 0.115N = 6 GBq / 0.115N = 5.21 × 10^17mass = (no. nuclei * mass number) / avogado number mass = (5.21 × 10^17 * 99) / 6.023×10^23mass = 8.18 × 10^-7 kg
 

Related to Radioactivity : mass of sample

1. What is radioactivity?

Radioactivity is the spontaneous emission of energy in the form of particles or electromagnetic waves from the nucleus of an atom. This process occurs because the nucleus of an atom is unstable and is trying to become more stable.

2. How is radioactivity measured?

Radioactivity is measured using a unit called the Becquerel (Bq). One Bq is equal to one nuclear disintegration per second. Another commonly used unit is the Curie (Ci), which is equal to 3.7 x 10^10 Bq.

3. What is the mass of a radioactive sample?

The mass of a radioactive sample refers to the total amount of material that is undergoing radioactive decay. This can vary depending on the specific isotope and its half-life, but it is typically measured in grams (g) or kilograms (kg).

4. How does the mass of a sample affect its radioactivity?

The mass of a sample does not directly affect its radioactivity. However, the larger the mass, the more radioactive particles will be present and the greater the amount of radiation emitted. This is why radioactive waste with a high mass can be more dangerous.

5. What is the relationship between half-life and mass in a radioactive sample?

The half-life of a radioactive substance is the amount of time it takes for half of the sample to decay. The mass of the sample does not affect the half-life, but a larger mass will have a longer total decay time than a smaller mass. This is because there are more atoms present, and therefore, more radioactive particles undergoing decay.

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