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A rate constant is found to have units L mol^-1 s^-1. What is the order of the reaction?
AFirst order
BZero order
CThird order
DSecond order
Answer & Solution
Correct answer: D. Second order
1. For an order-n reaction, units of k are $(\text{mol L}^{-1})^{1-n}\text{s}^{-1}$.
2. For second order ($n=2$): $(\text{mol L}^{-1})^{-1}\text{s}^{-1} = \text{L mol}^{-1}\text{s}^{-1}$.
3. This matches the given units, so the reaction is second order.
4. First order would be s^-1 and zero order mol L^-1 s^-1, neither matching.
_Source: NCERT Class 12 Chemistry Ch 3 "Chemical Kinetics", p.8_
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