A Sample Of Radioactive Material Has Mass 'm', Decay Constant Λ And Molecular Mass 'm'. If Na ​is Avogadro's Number, What Will Be The Initial Activity Of The Sample?

Sol:

We know that the activity of any radioactive material is λN,

where:

N is the number of undecayed nuclei at time t

λ is decay constant

We also know that N = N0e λt

where:

N0 = number of undecayed nuclei at t = 0s

λ N0 = initial activity

N0 = $$\frac{m}{M} * N_{A}$$

where:

m is the initial mass of the radioactive sample

M is the molecular mass of the sample.

Therefore, the initial activity = $$\lambda \frac{mN_{A}}{M}$$

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