Concentration of the limiting reactant (with initial concentration of a moles/litre) after time t is (a-x). Then ‘t’ for a first order reaction is given by____________________?
Correct answer: A
Explanation
For a first-order reaction, the integrated rate law is $\ln[a]_t / \ln[a]_0 = -kt$. Rearranging gives $t = (1/k) \cdot \ln(a_0/a_t)$, which matches option A.