$A$ reaction is first order with respect to $A$ and second order with respect to $B$. How many times the rate of reaction is affected on increasing the concentration of $B$ three times?

The differential form of the rate equation is given by:
$dx/dt = k[P][Q]^{0.5}[R]^{0.5}$
Which statement about the above equation is wrong?

The rate constant of a reaction is $1.388 \times 10^{-3} \ mol^{-2} \ L^{2} \ s^{-1}$. The order of the reaction is:

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 $2^{nd}$ order reaction $R \rightarrow P$,the following graph holds true. Identify the incorrect statement.

$A$ reaction $2NO + 2H_2 \longrightarrow N_2 + 2H_2O$ has the following mechanism:
Step-$I$: $2NO \longrightarrow N_2O_2$
Step-$II$: $N_2O_2 + H_2 \longrightarrow N_2O + H_2O$
Step-$III$: $N_2O + H_2 \longrightarrow N_2 + H_2O$
Which of the following substances is a reaction intermediate?