Fill in the blanks:
$(1)$ If $t_{1/2} = \frac{0.693}{k}$,then the order of reaction is .......... .
$(2)$ For a zero order reaction,$t_{1/2}$ is proportional to .......... of the initial concentration.
$(3)$ In a first order reaction,the rate of reaction is proportional to the .......... exponent of the concentration of the reactant.

Given below are two statements: $R = 8.314 \text{ J K}^{-1} \text{ mol}^{-1}$ and $1 \text{ cal} = 4.2 \text{ J}$.
Statement $I$: When $E_a = 12.6 \text{ kcal/mol}$,the room temperature rate constant is doubled by a $10 \text{ }^\circ\text{C}$ increase in temperature ($298 \text{ K}$ to $308 \text{ K}$).
Statement $II$: For a first-order reaction $A \to B$,the graph of half-life $(t_{1/2})$ versus initial concentration $[A]_o$ is a straight line passing through the origin.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following reaction mechanisms will have a fractional order with respect to $A_2$ or $B_2$?

Under identical reaction conditions,the concentration of a substance is $1.386 \ mol \ m^{-3}$. It is halved in $40 \ s$ and $20 \ s$ by first-order and zero-order kinetics,respectively. The ratio of the rate constants for the first-order $(k_1)$ and zero-order $(k_0)$ reactions,$\left( \frac{k_1}{k_0} \right)$,is ............ $m^3 \ mol^{-1}$.

The rate constant for the reaction $H_2 + I_2 \to 2HI$ is $k_1 = 49$. What is the rate constant for the reverse reaction $2HI \to H_2 + I_2$?

Which of the following relations is correct for the given reaction orders?