If the concentration is expressed in moles per litre,the unit of the rate constant for a first order reaction is

For a first-order reaction $A \rightarrow B$,if the rate constant is $k$ and the initial concentration of reactant $A$ is $0.5 \ M$,what is its half-life period?

For a first-order reaction,it takes $20 \, \text{min}$ for the concentration to decrease from $1 \, M$ to $0.6 \, M$. How much time is required for the concentration to decrease from $0.6 \, M$ to $0.36 \, M$?

Find the rate constant of a first-order reaction in $sec^{-1}$ having a half-life of $2.5 \ hours$.

Two first order reactions have half-lives in the ratio $3 : 2$. Calculate the ratio of time intervals $t_1 : t_2$ if $t_1$ is the time period for $25\%$ completion of the first reaction and $t_2$ for $75\%$ completion of the second reaction. (in $: 1$)

The rate constant of a reaction is $0.693 \times 10^{-2} \ min^{-1}$. What is the half-life period (in $s$)?