Which of the following is the fastest reaction?

$NO_2$ required for a reaction is produced by decomposition of $N_2 O_5$ in $CCl_4$ as per the equation $2 \, N_2 O_{5(g)} \rightarrow 4 NO_{2(g)} + O_{2(g)}$. The initial concentration of $N_2 O_5$ is $3 \, mol \, L^{-1}$ and it is $2.75 \, mol \, L^{-1}$ after $30 \, minutes$. The rate of formation of $NO_2$ is $x \times 10^{-3} \, mol \, L^{-1} \, min^{-1}$. The value of $x$ is . . . . . . .

For the chemical reaction $N_{2(g)} + 3 H_{2(g)} \rightleftharpoons 2 NH_{3(g)}$,the correct option is

Time required for completion of ionic reactions in comparison to molecular reactions is

For the reaction $\frac{1}{2} A \rightarrow 2B$,the rate of disappearance of $A$ is related to the rate of appearance of $B$ by which of the following expressions?

For a reaction,$2A + B \rightarrow 2C$,the rate of disappearance of $A$ is $0.076 \ mol \ dm^{-3} \ s^{-1}$. What is the rate of disappearance of $B$?