If half-life of a chemical reaction is 30 minutes, how much time is required for its 87.5% completion?
Correct answer: C. 90 min
- A. 30 min
- B. 60 min
- C. 90 min
- D. 120 min
Explanation
Fraction remaining=(1/2)nwhere n is the number of half lives.If 87.5% of the reaction is complete, this means 12.5% of the reactant remains. Therefore, we need to find 𝑛 such that (1/2)n =0.125Since0.125 can be rewritten as 1/8 thus (1/2)n = (1/2)3 Thus n=3 half-lives.Given that the half-life is 30 minutes, the total time for 3 half-lives is:Total time=n×Half-life=3×30 minutes=90 minutesTherefore, the time required for 87.5% completion of the reaction is 90 minutes.
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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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