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For a zero order reaction with initial concentration [R]0 = 0.50 mol L^-1 and rate constant k = 1.0 x 10^-2 mol L^-1 s^-1, what is the half-life?
A100 s
B50 s
C25 s
D69.3 s
Answer & Solution
Correct answer: C. 25 s
1. For zero order, $t_{1/2} = \dfrac{[R]_0}{2k}$.
2. $= \dfrac{0.50}{2\times1.0\times10^{-2}}$.
3. $= \dfrac{0.50}{0.02} = 25\ \text{s}$.
4. Distractor B forgets the factor 2; distractor D wrongly uses the first order formula 0.693/k.
_Source: NCERT Class 12 Chemistry Ch 3 "Chemical Kinetics", p.16_
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