The half-life of Iodine-131 is 8 days. If a sample has initial activity of 100 counts per minute, after 24 days the activity will be: MCQ with Answer and Explanation
The half-life of Iodine-131 is 8 days. If a sample has initial activity of 100 counts per minute, after 24 days the activity will be:
A. 25
B. 50
C. 12.5
D. 6.25
Answer: Option C
Solution (By JKSSB Mock Tests)
Number of half-lives = 24/8 = 3. Fraction remaining = (1/2)³ = 1/8. Activity = 100 × 1/8 = 12.5 counts per minute. Radioactive decay is exponential. After 1 half-life: 50, 2: 25, 3: 12.5. This isotope is used in thyroid treatment.
Explanation:
Calcination is the process of heating a concentrated ore strongly in the absence or limited supply of air. It is typically used for carbonate ores to drive off volatile impurities like CO₂ and H₂O (e.g., CaCO₃ → CaO + CO₂). Roasting is done in the presence of excess air.
Explanation:
Ethylene (C₂H₄) is systematically named ethene. The -ene suffix indicates a double bond. Ethane is C₂H₆, ethyne (acetylene) is C₂H₂, methane is CH₄. Ethene is an important petrochemical used to make polythene.
Explanation:
Sulphuric acid (H₂SO₄) was historically called oil of vitriol. Hydrochloric acid was muriatic acid, nitric acid was aqua fortis, carbolic acid is phenol.
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