The half-life of a substance in a certain enzyme-catalysed reaction is $138 \; s$. The time required for the concentration of the substance to fall from $1.28 \; mg \; L^{-1}$ to $0.04 \; mg \; L^{-1}$ is ....... $s$.

For a first-order reaction $A \rightarrow B$,the rate of reaction is $2.0 \times 10^{-5} \, mol \, L^{-1} \, s^{-1}$ when the concentration of the reactant is $0.01 \, M$. The half-life of the reaction is ........ seconds.

The value of rate constant for a first order reaction is $2.303 \times 10^{-2} \text{ s}^{-1}$. What will be the time required to reduce the concentration to $\frac{1}{10}$th of its initial concentration (in $\text{ s}$)?

The gaseous reaction $A_{(g)} \to 2B_{(g)} + C_{(g)}$ is a first-order reaction. If the initial pressure $P_A = 90 \ mm \ Hg$ and the total pressure after $10 \ min$ is $180 \ mm \ Hg$,calculate the rate constant of the reaction.

Half life of a first order reaction is $3 \ minute$. What is the time required to reduce the concentration of reactant by $90 \%$ of its initial concentration?

State whether the following sentences are true $(T)$ or false $(F)$.
$(a)$ The reaction of an ester with water produces an alcohol and an acid.
$(b)$ The concentration of water remains constant during the hydrolysis of an ester.
$(c)$ In the hydrolysis of an ester,$[H_2O]$ remains constant.