Which one of the following represents correctly the units of the rate constant k for a first order reaction?
Correct answer: A. s-1
- A. s-1
- B. mol.dm-3s-1
- C. mol dm-1s
- D. mol-1dm1s
Explanation
rate has units of, for example, mol dm^-3 s^-1 (concentration per unit time).k (rate constant) needs to have units that cancel out the units of [A] to give the correct units for rate.[A] (concentration of reactant A) has units of mol dm^-3 (moles per unit volume).In order to find the units of k : rate/ [A] = mol dm^-3 s^-1 / mol dm^-3 = s^-1 .Option A represents the correct unit for the rate constant for a first-order reaction. It implies that the rate constant is measured in inverse seconds (per second), which cancels out the units of concentration.
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Reaction kinetics relates reaction rate to concentration, temperature, surface area and catalysts. Questions cover rate laws, reaction order, rate constants, activation energy and the activated complex, including how a catalyst lowers the activation energy without changing the overall energy change or equilibrium position.
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