For the gaseous reaction $A(g) \longrightarrow B(g) + C(g) + D(g)$,starting with an initial pressure of $400 \ atm$. If the total pressure after $2 \ hr$ is $800 \ atm$,the value of the rate constant is: (consider the reaction to be $1^{st}$ order): (in $hr^{-1}$)

In a first order reaction,the ratio $\frac{a}{a-x}$ was found to be $8$ after $10 \, \text{min}$. The rate constant is:

$75\%$ of a first-order reaction was completed in $32 \text{ minutes}$. When was $50\%$ of the reaction completed? (in $\text{minutes}$)

Calculate the rate constant of a first-order reaction having a half-life of $1 \text{ minute } 40 \text{ seconds}$.

The following data were obtained during the first-order decomposition of $2 A_{(g)} \rightarrow B_{(g)} + C_{(s)}$ at a constant volume and at a particular temperature. The rate constant in $min^{-1}$ is:

$S$.no.	Time	Total pressure in Pascal
$1.$	At the end of $10 \ min$	$300$
$2.$	After completion	$200$

$t_{87.5}$ is the time required for the reaction to undergo $87.5 \%$ completion and $t_{50}$ is the time required for the reaction to undergo $50 \%$ completion. The relation between $t_{87.5}$ and $t_{50}$ for a first order reaction is $t_{87.5} = x \times t_{50}$. The value of $x$ is $......$. (Nearest integer)