Which of the following reactions end in finite time?

For a reaction,$A \rightarrow B$,the rate equation is $r = K[A]^0$. If the initial concentration of the reactant is $a \ mol \ dm^{-3}$,find the half-life time of the reaction.

For the reaction $R \rightarrow P$,the concentration of $R$ is measured as a function of time and the following data is obtained:

$[R] \ (M)$	$1.0$	$0.76$	$0.40$	$0.10$
$t \ (min)$	$0.0$	$0.05$	$0.12$	$0.18$

The order of the reaction is:

The reaction $A \to \text{Products}$ is a zero-order reaction. If the initial concentration of $A$ is $2 \ M$,then at time $t = 1/K$ (where $K$ is the rate constant),the concentration of $A$ will be ......... $M$.

If the rate of the reaction is equal to the rate constant,the order of the reaction is

The rate constant for a zero order reaction is $3 \times 10^{-2} \ mol \ L^{-1} \ s^{-1}$. After $25 \ s$,if the concentration of the reactant is $0.5 \ M$,then the initial concentration of the reactant is ............ $M$.