The units of the rate constant k for a first order reaction are
Correct answer: B. s-1
- A. mol dm-3 s-1
- B. s-1
- C. mol-1 dm3 s-1
- D. mol-2 dm6 s-1
Explanation
For a first order reaction rate equals k times concentration, so k must have units of rate divided by concentration, which reduces to reciprocal seconds. The units of k therefore change with the order, being mol dm-3 s-1 for zero order and mol-1 dm3 s-1 for second order. Checking the units is a quick way to confirm that an order has been deduced correctly.
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About Rate Constant
The rate constant, k, connects reaction rate with reactant concentrations in a rate law and has a value fixed for a particular reaction at a given temperature. Questions involve determining k from rate data, identifying its units for different reaction orders, and applying the Arrhenius equation to temperature changes.
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