Consider the general reaction nA → Product. The rate of equation for a reaction is given by rate of reaction = k [A]n. If the value of n = 2. Then the unit of k for the 2nd order of reaction is:
Correct answer: C. mol-1 dm3s-1
- A. mol dm-3s-1
- B. mol-2 dm6s-1
- C. mol-1 dm3s-1
- D. mol-1s-1
Explanation
Option C is correct.The rate constant (k) for a second-order reaction has units of mol-1 dm3 s-1. In a second-order reaction, the rate of reaction is proportional to the square of the concentration of one of the reactants. The rate constant (k) is a measure of the rate of reaction and is independent of the concentration of the reactants. To calculate the units of k, we can use the following equation: units of k = (units of concentration)² In the case of a second-order reaction, the units of concentration are mol dm-3. This gives us: units of k = (mol dm-3)²| Simplifying this gives us: units of k = mol-1 dm3 s1
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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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