For a second-order reaction where both reactants have the same initial concentration,it takes $500 \ s$ for the reaction to be $20\%$ complete. How many seconds will it take for the reaction to be $80\%$ complete (in $s$)?

For the reaction ${H_{2(g)} + I_{2(g)} \to 2HI_{(g)}}$,the possible mechanism is given below:
$I_2 \underset{k_{-1}}{\stackrel{k_1}{\rightleftharpoons}} 2 I$ (fast step)
${2I + H_2 \xrightarrow{K_2} 2HI}$ (slow step)
Determine the rate law for the reaction.

Which among the following is a false statement?

Consider the following reaction $A + B \rightarrow C$.
The time taken for $A$ to become $1/4$ of its initial concentration is twice the time taken to become $1/2$ of the same. Also,when the change of concentration of $B$ is plotted against time,the resulting graph gives a straight line with a negative slope and a positive intercept on the concentration axis. The overall order of the reaction is . . . . .

Find the rate law for the reaction,$CHCl_{3(g)} + Cl_{2(g)} \rightarrow CCl_{4(g)} + HCl_{(g)}$ if the order of reaction with respect to $CHCl_{3(g)}$ is $1$ and with respect to $Cl_{2(g)}$ is $1/2$.

What is the order of reaction if the unit of the rate constant is $s^{-1}$?