alleryActivity of 1 gram of ²²⁶Ra (Avogadro = 6 × 10²³; T₁/₂ = 1600 yr):
A10²³ Bq
B10⁵ Bq
CCannot determine
D≈ 3.7 × 10¹⁰ Bq (1 Ci, by definition)
Answer & Solution
Correct answer: D. ≈ 3.7 × 10¹⁰ Bq (1 Ci, by definition)
N = (1 g / 226 g/mol) × 6 × 10²³ ≈ 2.66 × 10²¹ atoms.
λ = 0.693 / (1600 × 365.25 × 86400) ≈ 1.37 × 10⁻¹¹ /s.
A = λN ≈ 3.65 × 10¹⁰ Bq ≈ 1 Ci.
(Original definition of curie.)
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