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JAMB Chemistry 2024 Paper

Question : 34

Total: 138

Solution:

Concept:

After each half-life, the mass of a radioactive element is reduced to half its previous value.

Explanation:

Find the number of half-lives that have passed:

n = \frac{200}{50} = 4

Use the decay relation:

Remaining mass

= \frac{\text{Original mass}}{2^n}

Substitute the values: Original mass

= 5 \, \mathrm{g}

n = 4

Remaining mass

= \frac{5}{2^4} = \frac{5}{16}

Remaining mass

= 0.3125 \, \mathrm{g} \approx 0.31 \, \mathrm{g}

Answer:

0.31 \, \mathrm{g}

Option D.

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