For a first order reaction, the plot of [A] versus time ( t ) gives a straight line with a slope of -0.0693 min ⁻¹ . The time required for 75 % completion of the reaction is ________ min .

Step-by-step solution

For a first order reaction, the integrated rate law is [A] = -kt + [A]₀ . The slope of the plot of [A] versus t is -k . Given slope = -0.0693 min ⁻¹ , so k = 0.0693 min ⁻¹ . The half-life of the reaction is: t_ 1/2 = 2 k = 0.693 0.0693 = 10 min . For 75 % completion, the amount of reactant remaining is 25 % , which is 1 4 of the initial amount. This corresponds to 2 half-lives ( n = 2 ). Time required = 2 t_ 1/2 = 2 10 = 20 min . Answer: 20