In which of the following order of reaction, the half-life is independent of initial concentration?
Correct answer: B. 1st order
- A. Zero order
- B. 1st order
- C. 2nd order
- D. 3rd order
Explanation
In a first-order reaction, the rate of the reaction is directly proportional to the concentration of the reactant. Mathematically, it's expressed as: Rate = k[A], where "k" is the rate constant and "[A]" is the concentration of the reactant. The integrated rate equation for a first-order reaction is ln([A]₀/[A]) = kt, where "[A]₀" is the initial concentration of the reactant. When solving for half-life, you get t1/2 = 0.693 / k, where "k" is the rate constant. As shown by this expression, the half-life of a first-order reaction is indeed independent of the initial 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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