alleryFor a first-order reaction, the time required for 99.9% completion is approximately:
A5 × t_(1/2)
B10 × t_(1/2)
C2 × t_(1/2)
D100 × t_(1/2)
Answer & Solution
Correct answer: B. 10 × t_(1/2)
**Show:** At 99.9% completion, [R]/[R]₀ = 0.001 = 10⁻³.
So t = (2.303/k) log(10³) = 6.909/k. And t_(1/2) = 0.693/k.
Ratio = 6.909/0.693 = **10**.
So **t (99.9%) = 10 × t_(1/2)**.
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