In which one of the following reactions,the rate constant has the unit $mol \ L^{-1} \ s^{-1}$?

For a zero-order reaction,the rate constant $K = 2 \times 10^{-2} \ mol \ L^{-1} \ s^{-1}$. If the concentration of the reactant after $25 \ s$ is $0.5 \ M$,then its initial concentration must be ...... $M$.

What is the concentration (in $mol \ L^{-1}$) of the product $B$ after $20 \ s$ in the following reaction? Given that $A \longrightarrow 3B$,rate $= k[A]^0$. The data is provided in the table below:
| Time $(s)$ | Concentration of reactant $A$ $(mol \ L^{-1})$ |
| :--- | :--- |
| $0$ | $0.1$ |
| $15$ | $0.05$ |
| $20$ | $0.1 - x$ |

Which of the following is the incorrect equation for the rate constant of a zero-order reaction?

The rate constant of the reaction $A \rightarrow B$ is $0.6 \times 10^{-3} \, mol \, L^{-1} \, s^{-1}.$ If the concentration of $A$ is $5 \, M,$ then the concentration of $B$ after $20$ minutes is ......... $M.$

For a reaction,doubling the concentration of the reactant doubles the half-life period. What is the order of the reaction?