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The disintegration of radioactive phosphorus to silicon follows the first order kinetics with rate constant...

Chemistry
JAMB 2025

The disintegration of radioactive phosphorus to silicon follows the first order kinetics with rate constant k\(_1\) = 3.85 x 10\(^{-3}\). Determine the half life of phosphorus.

  • A. 8 s
  • B. 180 s
  • C. 80 s
  • D. 100 s
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Correct Answer: Option B
Explanation

Firstly, State the formula for the half-life of a first-order reaction.

Radioactive decay follows first-order kinetics.

The half-life (t\(_{1/2}\)) for a first-order reaction is related to the rate constant (k) by the formula:

                                            t\(_{1/2}\) = \(\frac{ln 2}{k}\)

                                            t\(_{1/2}\) ≈ \(\frac{0.693}{k}\)


Secondly, calculate the half-life using the assumed rate constant  given in the question as k = 3.85 x 10\(^{-3}\)s\(^{-1}\)

                                            t\(_{1/2}\) = \(\frac{0.693}{3.85 x 10\(^{-3}}\)

                                            t\(_{1/2}\) = 180 s

There is an explanation video available below.


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Explanation Video

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